I haven’t seen this talked about, so I’m just going to ramble on about it for a moment.
A forced tech roll is what you think it is. It’s when you force your opponent to tech-roll backwards. Doing this prevents the opponent from teching straight up or forward and allows you to set up consistent follow-ups because you know how the opponent will recover from knockdown.
The general rule with forced techs is that they happen when your opponent’s hit by a C aerial. A 2-hit chain, such as j.B, j.C will cause a forced tech, but a 3-hit chain or more will cause a “fly-screen” knockdown that the opponent can follow-up with a back or forward tech-roll, or a neutral tech. Certain characters cannot cause forced techs or “fly-screen” due to the properties of their j.C’s (such as Saki and Megaman).
There are exceptions to the 2-hit limit, however. A relaunch is one example. Everytime you launch your opponent you “refresh” this 2-hit limit. Therefore characters with relaunch combos, like Chun or Y-1, could perform varied numbers of jumping attacks before their relaunch, after which the 2-hit limit is re-instilled and you can then perform a forced tech-roll knockdown.
Other exceptions are properties placed on certain moves. Y-1, for example, can follow a launch with a sj.B xx 623C, 6239C, air-dash sj.C. This will cause a forced tech-roll because Y-1’s 623 special doesn’t count towards this 2-hit limit. However, certain special moves do. If Joe the Condor was to perform a launch, into a sj.B xx A shuriken, air-dash sj.C, the opponent would fall w/ a “fly-screen” knockdown.
Another interesting thing about forced-tech rolls is that the opponent is still susceptible to OTG moves while they’re rolling backwards, meaning a Y-1 could follow up a forced tech with a comboable OTG super, even though the opponent looks like they’re recovering.
The reason you’d want to force a tech-roll is that you control where the opponent goes after your combo and you can pursue and pressure the opponent as you see fit. Some cases of forced tech-rolls, such as forcing a tech-roll in the corner, allows for ambiguous cross-up situations as well.
The downside to forced techs, however, is that you can’t perform any more then 2-hits after a launch, limiting your damage.
That’s all I really have to say about forced techs, it’s just something I haven’t seen discussed to any real extent and I randomly felt like discussing it.