I shoot .45 Colt in 2 Ubertis, a 19" '66 Yellowboy carbine and a 24" '73 Special Sporting rifle. I shoot 2 weights of plated bullets; a 255grn FP by X-Treme and a 200grn HP by Berry's. Plated bullets avoid the whole leading issue entirely and as long as you taper crimp them and don't over do it, they work great at even high velocities.
(I've shot 10s of thousands of plated bullets with great results. I also shoot Berry's 110grn plated .308 bullets in my M1 Carbine at 1,950fps as well as X-Treme 150grn plated .308 bullets in my 30-30 at over 2,000fps with great results so this whole internet hype of plating falling off at high velocities is mostly BS or the result of over crimping and cutting through the plating thus damaging the bullet.)
As my .45 Colt leverguns have the toggle link actions, I keep the pressures down to standard 14,000psi so I find that Unique works well with slightly under their stated max charges using standard LP primers for best accuracy. The 255grn out of my 24" rifle clock at a respectable 1,207fps.
As I shoot all of my long guns at the range at 200yds and 300yds, I find that these loads work well with acceptable accuracy for shooting steel plates, clay pigeons, etc. If I had a Rossi in .45 Colt I wouldn't hesitate to shoot them at Ruger Only level loads.
BTW, I also have 2 Rossis in .357mag; a 20" carbine and 24" rifle where I shoot both 158grn and 125grn plated bullets. I load them up with full charges of Lil'Gun with the 158grn with spectacular results with velocities out of the rifle at 2,005fps!! The 125grn are my plinking loads.