Nice work on this! I'm even more of a noob than you, but I have a few suggestions.
i always think timpani rolls and cymbal rolls are so over used in compositions
I'd suggest that they get overused because they are very effective when they are used appropriately. People don't always know when to say when, but like many things in the right context, there's nothing else like 'em. Except maybe whoosh-bangs.
start the midi line just before the bar/beat like maybe 1/16th, maybe that might work?
I can't speak to ASDR in Albion specifically, but scooting the midi note starts forward 10 or 20 milliseconds can do wonders for tightening up sound. I noticed the difference most towards the end with the perc hitting notes noticeably before the starts of the long string sustains.
i like cues with big percussion lines from the outset
I agree with the others that the percussion seems a bit inflexible. As with all dynamics, "big" is a matter of context, and if you start your piece quietly, any percussion (even somewhat quiet percussion) will sound big by comparison, while leaving the track some room to grow dynamically. It helps me to think of headroom as a finite thing and work back from the loudest I want to be.
Another option would be to grow it not in volume but in density. Add a layer or two of other big drums to the heavy impact beats only to give them extra weight. Add grace notes, little quieter drum strikes, a couple of 16ths or a few triplet 8ths ahead of the heavy impact beats. Fill out the silent beats with non-epic drums; it will add tons of texture and interest that is hard to even put your finger on. Daniel James is an expert at this.
If you don't want to do any of that, you can do like I did after about 2:30 of below, where I wrote a simple drum line, copied it, and panned one side hard left and one side hard right. Then I scooted the notes around on one side or the other just enough to add stereo depth and the illusion of bigness.