The others have told you want you want.

Give some thought as to where on the roof to place it. Generally speaking,
the HIGHER on the roof you make the holes the less likely water is to leak
in. And if you have it high on the roof if often doesn't make much
difference which side of the ridge it's on. If you don't care which side
then put it opposite the side the BIG WINDS come.

Once you decide what you want, I suggest you buy it yourself and make it a
part of the contract for the roofer to install it. It usually isn't a big
deal to install it after the fact but you have guys on the roof anyway so
....