Hardware (clamp and/or spacers) to mount a horizontal pipe to a roof?
Since this seems to be a temporary canopy, messing around with the roof's integrity (by adding a few attachments) is probably not desirable:  it will cause premature aging of the roof and increase the probability of a leak.  Obviously it can be done, for example solar panels on a roof, but that adds ongoing maintenance to make sure the fastening system is rain proof.

Why not mount the frame under the eaves?  Unless the roof joists are far apart, it probably isn't necessary to run a pipe across.  Instead, fasten each horizontal pipe from the canopy's top to a roof joist (if they are exposed) or to a hefty screw.  If the gutter is in the way, then just use some baling wire between the pipe and the screw.