Could be "Parkerifled" or could have been lined by just about anybody.
I would think that a good rook action could handle up to a 38 Special although the 32 H&R or 32 S&W may be closer to the original rook chamberings.
Also, look at the breech face and firing pin location. If it was modified for the rimfire .22, you may be better off running a 17HMR or similar. If the central firing pin was retained, then anything from 22 Hornet up to the smaller pistol cartridges would work out.