I'm gonna first assume that you don't have any 'protection' under your asbestos siding. That means you have something like gypsum board or some other form of sheathing. The bad news is that going with this assumption, the sheathing's only protection is the asbestos shingels themselves.
The BEST scenario is to have the shingles, or part of the shingles, around the window removed so there's 'room' to work on the window. BUT, if what you want to do is, basically, the same as what's there now, you needn't remove all or part of the shingles around the window. If you could do it all in a day (ie., fix the window and do the siding as part of the same 'job'), then the contractor can do what he needs to do knowing that siding is going up right after he's finished.
When I did our home, fortunately, the windows were already replaced. BUT, as I went along installing the vinyl, I primed and painted the windows, and capped them up with aluminum. (I know it sounds silly to prime, paint, and cap but this way, IF water gets underneath the capping, the wood won't rot.) And any wood along the way that was badly damaged, I replaced. (I replace 2 returns and 1 rake edge, and primed and painted them of course.) Soooo, I suggest you have the window issued addressed as the new siding job is done. The problem with your existing shingles is they're a bit of a pain to work with. They may be brittle, and you'll have to apply caulk too, only to have it all removed when you do the siding job. For me, we have 13 windows! That's why I waited to do any 'repairs' to the windows when I got to them during the siding job. I simply removed shingles a little at a time. (It was 20+ squares, or 2000 sq. ft. of siding.)
As for the roofing job, that can be done any time, IMO. If you live in a cold climate, consider Snow & Ice shield along the eaves. Consider a 30 year shingle too. Consider seamless gutters w/hidden hangers if you are getting new gutters. (Old gutters on a house with a new roof and siding, well, just won't look that nice.) Consider a ridge vent if you have an attic that's used for storage. Consider having soffit vents put in if you don't have them now.
When you get your new siding, consider having the contractor, for the time being, install additional electrical box 'accessories' and hose bibs IN ADDITION to electrical outlets and spiggots you have now. (It's nice to have outlets, for example, on all 4 sides of the house now.) (See Siding Accessories for Fixture Mounts and Vents, for example.) Just tell the contractor you want an 'electrical outlet here' and there, and 'you want a hose to go here, and there', and so on. Later on, someone can 'knock out' the mounts and such and install the outlets and piping for you. Just MAKE SURE the fixtures he chooses are MADE for outlets and spiggots! Outlets should be 'recessed' and, for example, spot light mounts are not recessed.
NOW you're a glutton for punishment! My best to ya and hope this helps.