Just a post to sum up what everyone has said about what to usually do after a df+rh connects. For some follow-ups I have added the damage & stun dealt while wearing the mask:
0/ Of course you just hit a normal attack to reset the opponent; for this I mostly use uf + fierce or ub + fierce. Or I use jab, and then df+roundhouse again to set-up a throw.
1/ Most obvious choice is RH Scarlet Terror if you don’t have meter (or don’t want to waste meter), it deals 240dmg & 300stun; and you can connect a super after if the opponent is cornered (but the timing is very strict)
2/ With meter, the other obvious choices are EX Scarlet Terror, which does 260dmg & 350stun
3/ EX Flying Barcelona Attack to Izuna Drop which deals 270dmg & 250stun; and prevents the opponent from quick-stand and thus opens the door to some “okizeme” game.
Most of the time, I stick with one the options already listed, but here are some less obvious follow-ups below:
4/ Another option is to slide. Opponents can’t quickroll after the slide; so like 3/, this is also good if you want to set-up some “okizeme” game
5/ You can also do a crouching strong, cancelled into (EX) Sky High Claw on the opposite wall; which can surprise the opponent
5/ So that next time you do crouching strong, you cancel it into a Flying Barcelona Attack on the opposite wall and then either slash left, right, izuna drop or escape
6&7/ Against some characters, you can walk a bit, hit jab and fadc the jab in order to dash under and cross up (works against vega, sagat; doesn’t work on blanka; haven’t tested against the rest of the cast); of course against these characters you can directly jab and fadc to stay on the same side.
8&9/ You can also choose not to hit and A/walk up a bit and df+forwad or B/ df+forward. Against an opponent who quickstands you’ll end up on the other side if you chose A/ and stay on the same side if you chose B/.