Quote Originally Posted by Cyclonite
All you need is a vent with a top, make sure the edges of the vent are raised 1/4" or so above roof level. Then secure a top that will overlap the edges of the vent a couple inches....you could always install a fake air register and pull air from the bottom of the attic through it also....you could also just use a vent that looks like an upside down J with the intake pointing toward the roof top.

Many options....don't forget to seal it up good.

Unless you have a large operation then don't worry about choppers, if that's too much to deal with for you then consider another hobby.
Make sure you install flashing as well and seal well with that nasty tar roof sealer. You don't need flashing, unless you want to keep water out.

And yeah, as long as you stay with just a few plants in a closet or something, you've got nothing to worry about. They are much more likely to look at your electric bill than your infared signiture. If your usage doesn't rise drastically and obviously, you don't have to worry.