I favor making my own antennas. For mobile it's difficult, getting small parts to hold well and attach to a proper mount. But at home you're open to whatever you want to do. Build a Yagi (dual band is tricky) or a Log Periodic for a beam, or try a quagi. Or one can build a simple dipole or ground plane for omnidirectional work. A vertical dipole for 2m with stubs for 70cm makes a decent dual band omni.
A word of caution when mounting the gable (the triangle on the side of the roof), driving lag screws into the house may not hold very well. It's typically just a panel of plywood. Reinforcement inside is highly recommended. Threaded rod with washer and nut on inside and outside makes it substantially more secure and if reinforced with some lumber inside much more secure.
A mast as in Tailgator's photo is how I'd go about it. This puts the downward weight on the ground. Mounts on the house now only support lateral forces, much easier on them. Rohn makes "tv" type mast, which is fine for modest antennas, in 16 gauge steel (as far as I know the one, others are 18).
Use the best coax you can afford. The last place one should skimp is feedline and it's often where hams do, $600 radio, $700 antenna, $25 unknown-hamfest coax.
Crummy RG58 (radio shack, no-name, cheap stuff that comes with the mobile mount, etc.) at 70cm, 100 feet of this stuff will lose almost 10dB. That's 50Watts from the radio will yield about 5 or 6Watts with a perfect antenna, worse if it doesn't match. You're better off standing on the roof with an HT. Times LMR400 (Belden 7810A, Jefatech LL400, others) will drop less than 3dB, about 27Watts into the antenna. Cut that in half, almost 38Watts. LMR600, a monster to work with, big expensive connectors, will drop less than 1dB over 50 feet.
It will be much better at 2m.