Ricoh KR mount means it is the K-mount that Pentax uses so yes it's probably going to mount and work right. However, you need to make sure that the lens does not have the dreaded "Ricoh pin" that will cause it to get stuck on the camera when it lodges into the slot for the screw-drive. It looks like this Ricoh lens doesn't have it though, since it looks like a purely manual lens. I've had a copy of this lens before and it didn't have the pin.
Once you've removed the offending pin (if any), you can mount it and use it like a Pentax-M lens. You have to set the custom function to permit use of aperture ring, and perform stop-down metering in Manual (M) mode by pressing the green button after selecting your desired aperture on the aperture ring. Or you can put the camera to Av mode but it will shoot the lens wide-open regardless of the aperture ring position.
Look for the pin as mentioned by Darrrr.
You can also 'destroy' the pin by stabbing at it until it lodges inside its recess and can no longer protrude out on the mount surface. Sticking it in with super glue or epoxy does the job as well.