Pole mount, if you have the room, has several advantages:
No leaks in the roof, ever!
You can absolutely nail down the direction, relative to true south, of the array, most roof installs are a compromise direction wise
No extra work when the structure needs re roofing
No climbing around up on a roof, during the install or "down the road"
Simplified regulations, because you are not messing with a structure people live in, less odds and ends needed due to fire regulations as compared to pole mount
Built high enough, they can be placed ABOVE the trees
The arrays run measurably cooler OFF a roof, this increases the power production, significantly
They are "portable", if need be, a crane can be called in, and the install process reversed. The part of the vert pole that is in concrete is cut off flush with the ground and left as is. The above ground part of the vert pole is welded onto a new in ground pole (by a welder who knows what he's doing)
They can be designed to be rotated down, to a more vertical position, so in the winter snow slides off better and they are aimed more at the sun.
I've transported these pre assembled arrays hundreds of miles, using my pickup truck, and/or a trailer, and a local crane service. I don't use trackers, store bought trackers, anymore. Solar has gotten too cheap.....I tell my customers it is cheaper to not pay the high expense of a tracker, and just buy more PV. Plus you now have a bullet proof installation, with NO moving parts, for this same reason I rarely provide tilt capability anymore on the racks I build "just buy more solar", weld it down solid, and forget about it.
Some pictures of a few that I have fabricated and installed. I do all the work in my shop, at my convenience, and then then truck them to the job site. Using my crane (not bought for doing just solar work I do all types of general crane work with solar as a sideline) I can lift (my racks are designed to be lifted, with dedicated pick points, the modules are pre wired on the back side) these arrays and set them on the vert pole in minutes. I of course install the vert poles a couple weeks earlier. I use pipe i find from a salvage yard when possible, I often go with larger dia. then I need, just because I got it cheaper then new pipe of a smaller size. Doing it this way, I can beat any "store bought" pole mount rack, not to mention they arrive via motor freight ($$) need to be assembled on site (labor intensive) and only then can the modules be installed, one at a time, all on site. So lots of work and time on site, my way, I can pull in at 8 and easily be done by 10. What I usually do is is run the cabling to the pole mounted disconnect, then turn the rest of the job over to a conventional licensed electrician. These are grid tied system, but I've done it the same way for off grid install, though somewhat smaller.