couple things to note here, the first is dont be afraid to change key when transitioning to a new part! It can really open up other parts of the song.
But my first suggestion beyond that is that if you are wanting to not change the key too much you can do things like transition to the relative minor or something. IE First riff in C Major then work into A minor. Same chords but you can get unique progressions out of both of them when actually thinking of them as C major and A minor separately and not just the chords that make them up.
Second, If you are not wanting to change into a different key, think of using a completely different chord progresion within the same key ie a jazz ii-V-I sounds very different than a "50s" I-vi-IV-V7-I (and yes both of these can still sound good with the distortion on). So even though you are using the same chords, once again you can get an entirely different sound.
My third suggestion would be adding chords in besides the obvious. Remember that there are a LOT of chords available to you within one key, not just your Major and Minor chords! (diminished can be your friends). Sure you have your I, ii, iii, IV, V, vi, (VIIdim) but dont forget using the extended chords built off of these:
minor 7ths, major 7ths, dom 7ths, major-minor 7ths, 6ths, 9s etc etc and also the different types of diminished chords available to you. So you could use a basic progression and then switch to something using some extended chords.
fourth, along the same kind of lines, remember two other big things 1) substitutions 2) there are several other chords NOT in your key that will work within a progression in your key (did that make sense to you) . tritone substitutions, and secondary dominants add chords that arent normally/technically in your key but flow seamlessly when placed before/after the right chords that actually ARE in your key.
Change time signatures, this can add a totally different dynamic to your song, and even within the same key you can have a riff that sounds entirely different but still transitions well.
lastly, ill stress again, dont be afraid to change keys
