My rossi in .357 does not like .38 spl wad cutters, or hollow points, but it will feed round nose fine.
Feeds every .357 I have tried, so it may be a function of the shape or length of the rounds you have.
When I brought it home all I had were .38s and i was really upset, but after playing with round nose and .357 i love the gun.
It does not like Blazer ALUMINUM rounds, they will hang up in Magazine tube..so be wary of that, too.
Hope you get it straightened out.
You might look at
www.leverguns.com too. Lots of info there on the Rossi/Pumas.
Mark