Rowland is not as critical as Clark. Clark says not to try to fire .45ACP ammo in a .460 barrel, because since the round head spaces on the mouth of the case, instead of the rim (rimless cartridges). This makes the relationship much different than that between a .44 Special/.44 mag or .36 Special/.357 mag. As mentioned, the .45 might not even fire if the extractor doesn't hold the cartridge in place. Even if it does fire, performance might be spotty.
As to the reloading dies, yes, .45ACP dies, as well as primers and bullets, will work for the Rowland. I have a Springfield Mi Spec with a Clark conversion barrel that works very well, shoots accurately. Most I've pushed a hand load to so far is a 200 XTP to 1340 fps, and there is a lot more to go.
