We don't know anything about your D&D but you expect us to give recommendations? Know how your equipment works, know the venue, know the flow of activities, know some basic ideas of composition, know what shots are expected from you, know which shots you want to add as personal note ... Look how much equipment considerations are really needed.
This is a very big assumption (and to me shows quite a bit of arrogance/lack of insight). You don't know how dark it is. What if you are shooting at ISO 3200, 6400 and it's totally grainy? What if you are using the biggest aperture, then your DOF is too thin? What if even then your shutter speed is too slow and you get a lot of motion blur?
Why do you think pro events photogs, with D700, D3S, etc, still use flash?
Its a bad assumption to think that a low light performance camera will deliver in low light conditions.
Cause it will not.
You need 1/60 at least to have a reasonable chance of preventing motion blur and probably around 1/125 to do it really reliably.
This puts a strain on the iso needed, bumping up the iso.
Then you need a reasonable f-stop to have DOF, yes you'd want that to keep ppl looking in focus and help in focus shift due to subject shifts.
Again, that puts a strain on iso and it needs to go up again.
Know more about your camera too, which comes with practice and read up.
I can give you a 'formula' but it would be irresponsible to do so.
Reason is that it would only work in certain situations and if your conditions are not the same, it may not work.
1. Set camera to M.
2. Expose for the ambient. Guideline is to keep a shutter speed that stops movement and camera shake (eg. 1/80). Iso keep a reasonable iso that is not too noisy and retains detail (eg. Iso 800 or 1000, 1600). F-stop should give reasonable dof too, eg. 2.8, 4.
3. Power on flash on ttl mode. If your flash is smart enough in ttl mode it should expose your subject properly. Adjust flash power compensation to taste. (Nikon flash system supposed to be the best in business). If ceiling is low enough, you can bounce the flash for more flattering and softer light.
i second this. if you think that you don't need a flash unit, then you're screwed. the lighting will most probably be erratic, and some places will have too many shadows. do you want pictures with horrible shadows, some people lit while others aren't?
if you're not the assigned photographer, just bring a compact. go and enjoy yourself.
I am using a D7000 too... and helped my friend as a backup PG (i am his "brother" and he have hired the main PG) to assist the main PG (if needed) and to shoot candids as the main PG may not be able to cover every area of the wedding dinner...
so I assume that your DnD is held in a ball room or a large function room in some hotel... and i can tell you that the lighting is actually quite dim to the camera although the place may look bright to your eyes... dun be suprised that you may be shooting at >ISO1600 without flash at your preferred apperture and handheld shutter speed settings... a flash unit will help you shoot at your preferred settings at a much lower ISO...
and the lighting conditions will vary at different spots of the ballroom due to wall lamps and ceiling lights... a flash unit will help you override the inconsistant lighting conditions...
If you are not going to use a flash and rely on bumping ISO... you may get a well composed but noisy photo... why not bring along a flash and get a better composed photo that is less noisy?
Would advise using a flash. It'll come in handy freezing movement and for when you've to stop down to f/8 etc for group shots. Without flash at f/8 in an indoor environment, you're going to have slow(er) shutter speeds. Slow shutter speed + handshake (not the congratulatory kind) = recipe for disaster.
If you've a wide-to-semi tele zoom lens, use that as well, it may be able to let you react faster to get your shots and capture more moments.
What is the lighting condition, where will you be doing the shoot, what type of shoot do you want to achieve (group shots, people moving around, action shots - for games and stuff, models doing catwalk, what?), what is the place you want to shoot - outdoor or indoor, what is the environment like - shady, low ceiling, high ceiling, no ceiling, bright sunlight, no sunlight, daytime, nighttime, what?
And to limit yourself against using flashes is the silliest idea I have ever heard, no matter how good your camera can handle lowlight photography... note that noise can be included into ur photo without too much of a problem with any post processing, but to remove them completely is a problem altogether - because you might lost details in your photos.
other than "light" issues....
shooting with a 50mm prime lens probably isn't such a good idea when you shoot in indoor, confined space and dynamic environment, especially when you have no experience shooting an event.
Don't be silly, that is a fallacy. Technology has not reach that stage yet. Besides getting good pictures, let alone composition, is not about the low light capability of the camera. I am sure photographers that did events will agree. It is about the ratio of lights. Even if your camera can capture details in clubs at iso 100000 with the quality of iso100 compared to now, the face of your subject still looks dark in comparison to the surrounding if the surrounding is brighter. Not everyone like to look dull in front of the camera. Having a flash in all occasion to lit up the shadow area appropriately is a must no matter how technology progress.
If you are doing event, use a flash, keep your large aperture lens because you will be doing more group shoots than portrait shoots. Use a zoom because it will help a lot in constraint spaces in between furnitures for where you stand. Your audience is not interested to wait for you slowly change your lens, zoom at 2.8 will save your evening, not your day.
Even day time photographers use flash to control the ration of lights falling on the subject. Pro cameras don't come with build in flash, because you are expected to mount one. An a big one to throw all the light necessary to achieve your objective. Not that I am a pro, but flash is like 100% a must and seriously I say it is more important than having the best lens.