While a roof mount tower and antenna is a decent load, it is still within the design spec's of most modern roofs for "Dead Load Rating". Would I put that much weight on a roof? No. Even with it spaced out over various roof joists/rafters, it would far exceed that dead load rating for the roof. and then the added weight of that snow and, well, it would be pretty cold in that house just long enough for you to tell the owner what happened and why. Then your only heat would be from your car's heating system.....
Please, and seriously, do NOT put that much weight on the roof unless the owner had it fortified and built with concrete with a design load far exceeding what you intend to do.
Just my .02
Now, an old truck rim laying flat on its side on top of a sheet of that 1" MDF, with a piece of heavy gauge pipe welded vertically into the center of the rim might work. Just mount the antenna on the mast, get the guy wires attached at predetermined heights on the mast and the antenna. Anchor two of the three guys and use the third to pull the assembly up. Then anchor the last guys on that third side. That should get you close. Might not be a permanent solution, but there are many others that have some ideas and info all over the internet.