Disguiser is supposed to swap the ti results for all tis, as far as I understood. But this is how I've seen it work with each ti role.
Spy-works, but unless you disguise yourself, it'll show an extra visit, thereby confirming that one of the maf visits are maf, and that there is a dis in the game.
Inv-works, but inv is already a weak role, and since you can't disguise anyone but yourself if there is a spy present, you'll out yourself more often than not if an inv is on you, especially if you decide to pretend to be doc on jailor in case lo.
Sheriff-works, but sheriff is also a weak role already, and town ignores them half the time anyway.
Lookout-Doesn't work. By all rights, disguising yourself with the real tp should show you visiting jailor, and the tp not. Instead, it does nothing, and the tp will visit as usual. Considering lo is the most op ti, this is the one it SHOULD work with the best.
Coven roles
Tracker-Literally sees disguiser visit twice. Easy out, if town even half understands disguiser.
Psychic-Hard to tell, but I'm assuming it doesn't work, considering psy doesn't target anyone.
So disguiser only works on the worst two tis, while the two op ti roles either benefit from disguiser visits, or are barely affected. And not that they need buffs with the state of town, but sheriff and inv are the only two ti roles that most trickery rms even seem to affect.