I look forward to the responses. It may be that a standing seam metal roof where the PV panels can be clamped into place without any fastener penetrations into your roof might be a candidate for "best".

Depending on the point of view.

Since most roofs are asphalt shingled, solar installers would be very familiar with the installation. Some prefer to work with asphalt shingled roofs.

Metal shingle roofs require more care, but will last much longer than asphalt shingles and reduce the solar heat gain in the attic.

Clay tile roofs could be really problematic for some solar installers.

In any case, the mounts have to be treated as plumbing vents and flashed accordingly.

For metal shingle roofs, there are no direct penetration mounts which can be used. The fasteners are not exposed at all.

Standing seam roofs with non penetrating mounts are also a very good option.

If you're concerned about the solar heat gain, use a cooler color or more IR reflective roof material.

Solar electric generation also declines with increased temperature.

You could have the mounts installed first. In some counties, new homes have to be constructed PV ready - mounts are required.

Think about durability of the roof. You want your roof to last longer than your solar panels, as you don't want to have to remove the panels, then change the roof and reinstall the panels...that's a lot of work. We have a 50 yr asphalt shingle roof under ours.

I would always go metal in these applications.

Its permanent and the metal roof will keep the surface temperatures lower as compared to asphalt over the length of the day.

The thin film solar applications for standing seam don't have near the efficiency of the panel systems.

Just a note...

We had a skylight installed in a cathedral ceiling in our master bedroom,
(open beam with no attic space)

This was right over our bed and turned out to be a poor idea.

In addition to the bright full moons the rain was very noisey.
We had it removed.

Wonder how loud rain might be on a metal roof?

This post was edited by bukzin on Wed, May 21, 14 at 9:49

Not a problem.

Most metal roofing solutions are stone coated which helps deaden the sound.
The tiles are laid on top of a fairly solid and thick plywood or osb subroof with the requisite waterproofing membrane in between. Depending on the manufacturer's instructions, the tiles could be installed with or without battens.
In addition, there will usually be an insulated attic space.

For standing seam roofs, the metal will be backed by plywood or osb with a waterproofing under layment between which deadens the sound.

On the other hand, if the roof is corrugated sheet metal with minimal support and no insulating barrier separating the usual living space,yes, it will be noisy.

>> Wonder how loud rain might be on a metal roof?

Wonderfully loud, and actually soothing. Yes, I have lived in a corrugated metal roof house with terrible insulation where the terne was laid on lath, vaguely like barrel tile.

Actually, since there are so many things that can come between a metal skin and your bedroom ceiling, one can't really answer that question in any meaningful way without a lot of details, but in a nutshell, davidtay's answer is gold..