No one has answered my question about the mast itself. Does it rest on the roof, and if so, what do I need to put under it?
The problem with letting it sit of the roof itself, it will eventually 'eat' it's way through the shingles. You can place a piece of metal there to prevent this, securing and 'taring' it to the shingle or as ctdish
stated use the 'hook' below the spreaders to 'hang' the mast.
I have tried using lag bolts through the roof plywood and after a while they pull out and the antenna falls over.
If the lag screws could catch the 2 by 4's, it might work, but the legs don't seem to be the correct for the spacing for that.
If you are lucky you may 'catch' one rafter, but the solution is;
Place your tripod run one lag bolt in for each leg.
Go into the attic and 'hunt' for those bolts, mark the spots between the rafters and cut lengths of 2 x 4's to wedge between those rafters.
Pre-drill holes for two bolts per leg (I don't see reason for all three if you do it this way).
Using a longer lag bolt through those holes will secure that tripod with little or no fear of the feet pulling out. It's more of a chance those rivets for the right angle brackets will let go than those lags pulling out unless you are in tornado alley.
My antenna is on the apex of our roof, on a 15' mast held in place with 3 sets of guys wires, and has been in place for almost 30 years. The guy wires are held in place with bolts attached thru the roof (metal) to the support studs underneath.
My tripod has been there for probably 35 years with guy lines. I did replace the anchors recently due to age and initial poor placement.
The other "maintenance item I do is coat all metal parts with clear acrylic spray to prolong them from rusting. I usually do it once a year.
Take a look here. This example is a typical untreated tripod after 15 or so years;
Though not completely related, look here also;