Well, blues follows a chord pattern, and rock is a bit more vague. Both use I, IV and V mainly, but sometimes other chords.
12-bar Blues consists of 3 lines of 4 bars each. Here is the base pattern:
I I I I | IV IV I I | V V I I
There are many variations on this.
I I I I | IV IV I I | V IV (or V7) I I
I IV I I | IV IV I I | V IV (or V7) I I
You can also add sevenths to this to end up with something like this:
I IV I I7 | IV IV7 I I7 | V IV I V7 (when the last bar contains the dominant chord, it leads into the next verse)
Rock goes into a bit more stuff, but usually you'd just be using your I, IV, V and occasionally ii and vi. With sevenths.
Pop, as we all know, follows a simple 4-bar progression - I, V, vi, IV. This may be mixed up.