you really do want the solar panel in full sunlight, so roof mount is best,
absolute best is on a mount that allows you to point it at the sun, the pole mount is good,
basicaly do all you can to ensure the panel has an unobstructed view of the sun, the cheaper pannels are really fussy about that, some if more than a few individual cells are in the shade the entire panel stops working, the more expensive ones reduce output,
i have 3 large (125 watt) panels on my motorhome roof, when i first put them on, one of them got shaded by the sattelite dish if the sun was shining from the left hand side of the van, that really dropped the output, so much that i'd turn the van around,
i since moved that panel, and get a nice 25 amp hours of charge on a sunny day... shame we dont get many of them here in england, we need panels that run off rain really
i really do need that much solar power for my motorhome, got waaaay too many toys in it that suck power, the fridge freezer alone uses 85 amp hours a day,
that's one of the reasons i want to build a tear, back to basics camping.