Ken,
I told you about the cast Remington rolling block kits, these are rough castings which require fitting, drilling and such. One thing easier about building a rolling block is that the breech block mortise that is tricky to cut and fit in a falling block rifle isn't near as hairy in a rolling block. The holes that you drill for the breech block and the hammer pins are marked on the sides of the receiver. the only thing in the receiver mortise that is tricky is just to get the width right, so the hammer and block don't move from side to side. The mortise in the castings is usually pretty close. A few files with safe edges and flats will do a good job. Fitting the breech block to the hammer takes a little head scratching but isn't too difficult.
Now if you want to really build one from scratch, I may be able to fix you up,. Another friend of mine, did have a peice of 4140 laying on a shelf near his work bench that someone started to machine a rolling block action from., I think it was the guy who makes the casting sets. I can probably get it for peanuts. Now that would be a in shop complete build.
Mashburn
David a. Cogburn