Ambrus, I think you are mistaken. My understanding is that rotoscoping is a technique whereby live action footage is painted over, in order to achieve animation. Ralph Bakshi's animated lord of the rings used the technique extensively. Another example is in The Empire Strikes Back. When Luke Skywalker first surveys his surroundings, having landed on Dagobah/Degobah - Yoda's home planet I can't remember the spelling of - a fantastical bird swoops through the scene. A real bird was released on the set and allowed to fly across it. The animators then went over the footage, creating their extra-terrestrial avian, fame by frame, matting out the real bird.
Not that this helps you, Xath, although, like Ambrus, I am a little confused by the wording of your question. 'Superimposing facial movement onto a still picture' would mean the picture wasn't still any more. It simply sounds like animation. I'm sure that's not what you're looking for, especially as you mention vocal effects as well. If there is a single word to describe the combination of these things, I am unaware of it. I used to be quite the SPFX buff, but that was in the days when motion control was a revolutionary technique and quad-optical printing was a thing of the future. So, sorry I can't help but I'd be interested to know the term you're looking for. Come back and share, if you find the answer elsewhere.