Forget about the roof mount for two reasons:
1) That will "break the bank".
2) If you park under tree cover, you won't have TV.
If you want an automatic solution, buy the
VuCube. Note that this will only deliver standard-def TV (not HD).
If you want more flexibility and lower cost, you can buy a satellite dish and tripod on eBay or Craig's List for <$100 and just learn to aim it yourself. Many of us do.
Either way, if you have a smartphone, you'll want to get a "satellite finder" app such as "Dish Pointer AR" or "Satellite AR" to help you in the process.
What receiver model do you plan to take from home?