The roof is the best bet reception wise, but can be the most difficult. An alternative to that or the attic option is to mount it to one end of a thin-walled galvanized pole (2.25" O.D. or smaller, 16 ft. long) that's available at your local mega-chain home improvement center. Use U-bolts to mount antenna to pole. Plumb bob or use level to fasten'to side of house or porch. Plumbing or pipe straps work well to snug up to roof line (I fastened to the fascia). The bottom of the pole can be set in the ground with concrete, or set in the dirt. I used a concrete block set in the dirt.

boom length - 18.25 in.
max width - 34.5 in.
vertical height - 18.25 in.
weight - 4.4 lbs.

from Winegard website specs

The attic option is better than indoor types (rabbit ears), but less so than the roof option. That said, I say go for the attic. You may have to do several adjustments to find the "sweet spot" for all (or most) of your channels. I would consider a more powerful antenna (size limits noted) to offset the slight loss of signal compared to the roof mount. Or maybe a line amplifier (Stuff-Mart or Radio Shaft) at the antenna would help pull in more stations and clear up any weak signals.

Good Luck!