It looks like I am going to experiment this way:
1) 38 cases - they can be crimped in the crimp groove without being too long to fit in 38's. Load mild with 231 and work up to max loads. No 296 I guess.
2) 357 - crimp on the top drive band - load using 296 eventually
3) Trim some 357 cases to crimp in the crimp groove and still be OK to fit the 357. Use 296
4) 357 cases and crimp in the crimp groove and shoot them in the Rossi 92 (if they fit) - 296
Many thanks to all for the ideas!