As posted by me previously, I have a nice original sporting roller that I had thought about converting to cf. Most folks here said to leave it be and shoot it with 44rf cases from DGW. So, I got cases, 22 primer shells, round balls correctly sized for bore diameter and some 3f black. Went to friends place in Maine, put target at fifty yds. Sights were difficult to pick up, the day was bright sun, no wind. Five shots were all over the target, friend tried, same result. Moved target closer, about twenty five yards, best group was four inches. We both agreed the sights were too fine, the rear aperture is too small, as is the front bead. Chambering, extraction, set trigger operation were all excellent. Plus, shooting an original roller is the best! Reloading the spent shells is a major PITA!!! So, what I'm wondering is, should I install a modern tang sight and a lyman 17 to get a better sight picture, or is a four inch group normal for these jury rigged rf loads?

I'd say a 4" group at 50 yds. with round balls would be very good. But I agree that a proper sized grease groove bullet will likely cut those groups in half. 
The PITA of dealing with those adapter cases is what made me convert mine. It's not original anymore, but I shoot it a whole lot more, and much more accurately.

You might try adding a drop of day-glo orange paint to the bead in the globe of the Beach sight and using the V notch. Doesn't someone like Buffalo Arms have a box of bullets you could get?

Vall, was the rf rolling block chambered for the 44 Rem (a cf?) or the 44 Henry rf? The Henry was a .446 or .440, 200 grain or 216 grain. Gunpowfun, what is your rifle's groove size? Old West Bullet Moulds has a .44 Henry flat 200gr .440"dia bullet 418"dia heel double cavity mould if the groove size is .440.

Or for a mould, maybe this one: (You need to Login or Register to view media files and links)

Sure wont break my heart that you're making it more usable. And the .40-65 is a good choice too. Might not be a period caliber for Rolling Blocks, but it's easy to buy brass, components, and dies for. And it does well at very long distances with the right twist rate and bullet.
But you'll want to get some good sights for accurate shooting at anything over 100 yds. Probably need the tang D&T for a good tang sight too.

1.937" spacing. The Lee Shaver Economy Soule would work well, and at $225 be a good sight. If you get into really serious competition you'd want a MVA, Baldwin, or Kelley Soule.