There are basically 3 systems
Dome
Roof mounted dish
Ground mounted dish
All 3 have advantages and disadvantages
Domes are solo LNB (Single or dual, but just one of them) this means they can see ONE satellite at a time,, Some of them are capable of rapidly switching from one bird to another and thus work well with a DISH NETWORK receiver, both sd and hd, but ... Read on.. Some work in motion, others do not.
A SINGLE can run ONE and only one receiver A DUAL can run multiple receivers or a DVR (Dual means dual output) however with DISH, you are restricted to one satellite at a time.
With DirecTV,, you can get SD (Non-HD) transmissions off 101 but NOT the HD transmissions on the other two KA band birds (Different frequency band, the LNB is not compatable)
Rooftop DISH... With a rooftop DISH you can only use it when parked, However since you buy the dish that matches the Sat-TV service you subscribe to there is no problem with either DirecTV or DISHnetwork, either SD or HD, because you buy the proper Dish.
ALL ROOF TOP systems==== Do not work if you are parked under the evil signal eating tree.. Thus I recommend a cheap A/B switch in the LNB line(s) A=the dome/dish on the roof up A-bove, and b is for a connector in the Basement or Bulkhead down B-elow.
Ground mount dishes.. See rooftop dishes for what they can do plus if you have enough cable you can set them up out away from the evil signal eating tree (Thank you Charlie Brown for the tree name)
Disadvantage: Storage and set up. Additional advantage COST! (Almost none)