Depending on the thickness of the aluminum you're using, and what all you're going to have on the roof (air-conditioners, tv antenna, roof vents, etc,... you may not need to worry about glue.
I used .030", have 2 roof airs' 3 vents, amp tv antenna, 4 solar panels, etc,...so it's pretty well fastened out in the middle.
If you do want it fastened down,...counter-top contact cement should hold just fine.
__________________
|