Cadence drills are optional but are incorporated in the workout texts for some workouts, you can search the workouts section (Log In to TrainerRoad) for “Cadence” or “ILT” (= isolated leg training). There has been quite a lot of debate whether changing your cadence is a thing you would want to do though, I think it leans more towards just using your natural selected cadence.
And what would you want to use the webcam for? Only thing I can think of is for a better bike fit and analysing your knee tracking or ankle flexion?