The best of both worlds is to have a large bore centerfire in the rolling block, and make an insert liner in .22 lr.  You can insert the liner and change the extractor, and breech block and have a .22 in your centerfire rifle.  You can generally get spare breech blocks for the conversion from Kenn at rolingblockparts.com

I have two of them done that way.  One, I had an original .22 rf block and I just used it, although I had to make a bushing to repair old primer erosion anyway.  The other, I had John King bush and rework for .22 rf.  I made the liners myself, by turning a steel case the size of the cartridge, and then bored it out and soldered in a liner.  

I use teflon tubing from McMaster Carr to center the liner in my rifle barrel.  Cut the tubing into about 1 inch pieces, and space them at unequal distances along the liner.  Move the spacers to tune the barrel; by trial and error you can find the configuration that shoots best.  My liner in my rolling block is capable of similar accuracy to my Lilja barreled Ballard.

Sometimes we overlook the obvious answers. I can turn the barrel with the shank offset which would be easier than making a bushing. 

Marlinguy - I am interested in how the six o'clock extractor was made to operate. Can you share some pictures of the extractor and breech block?

So I eded up with an action that someone machined down so light that I didn't think it would be safe with any centerfire. I also found in my collection of barrel a heavy octagon 22 barrel with a 1 in 20 twist. I had tried the barrel as a 22 hornet and it did not shoot very well. So the action and barrel became the start for a 22 short. The extractor has two 1/8" pins that slide in hole in the barrel. Trying to figure out a way to make it an ejector. I used a new breach block casting so there is no problem putting the firing pin where it needs to be, I cut a groove in the bottom of the breach block for  lever that works the extractor. Someday I will get around to finish it.