For suitable loads for your .45 Colt Rossi, try searching the Web for articles by John Taffin and Paco Kelly. Both are huge fans of the .45 Colt in revolvers and lever actions using pistol loads.
Other posters have described feral pigs and even bears taken using this caliber combination.
As you know, Rossi also chambers this rifle in the .454 Casull caliber. This is a quantum leap over .45 Colt power and capability when you are comparing factory loads. I personally do not hotload this caliber, but if you choose to, Taffin and Kelly will have the info.