Neither Dish nor DirecTV have a single DVR that will output HD to two different HDTVs and give them unique viewing experiences.
You can use the HDMI to one HDTV and the component to another HDTV, but each HDTV would have to watch the same channel.
The only other option would be either the Dish Hopper/Joey configuration OR if you went to DirecTV they might have a multi-room-viewing config that works but I don't know as much about their equipment to say.
IF you stick with Dish, I would either get another 722 or similar receiver for the other room OR go with a Hopper + a Joey.
It depends on how you want to view things in the two rooms as to what would work best for you.
A 722 has two SAT tuners + 1 OTA tuner... so if you put another 722 in the other room, each room has 2 SAT tuners and 1 OTA tuner. The only way to share content would be an external archive drive and you'd physically have to move that from room to room.
The alternative...
A Hopper in the main room and a Joey in the other room. Hoppers have 3 SAT tuners and currently no OTA capability. Joeys have no tuners but you can watch any of the 3 available tuners on the Hopper, any DVR content on the Hopper, and anything on an external drive connected to the Hopper.
If you don't need OTA, the Hopper/Joey setup is the better configuration for you I think.