I relate the ROA's most closely to the Colt Dragoon-series 44s, owing to their respective charge weight specs being so close to one another. Both will fit 35-40 grains of 3F BP behind a 44 caliber RB; the Walkers could hold 60 grains, and my 1860 repros were full at 28 grains.
I had a Ruger Super Blackhawk and a Third Model Dragoon at the same time, their weights were pretty close to one another.