The use of cast bullets in the ROA is old hat,tho the use of plated is new to me ,I have used wadcutters designed for 45 acp as cast; not sized, with good but not spectacular results. Undersized bullets will not seal the chamber(chainfire),nor would recoil allow them to stay seated in chambers as pistol was fired. Cast bullets are available that are suited for this application if y'all arent interested in casting your own, find a style you like in .453-.454 ....I would bet the plated will be .451. I would use wads either of felt or wax under the bullet. The Ruger is the primo blackpowder revolver available toss what you have and feed it well! There is no good reason to use undersized bullets, and many not to! Good Luck
robert