Make sure you look at the Turbo Tents:
Turbo Tent
Extremely fast pitch (second only to an Oz Tent, which doesn't break down very compactly), lots of size options. So far ours is holding up very well. There's a short review in the Fall 2009 Overland Journal.
Im glad that there are a number of you that agree. The RTT is the quintessential expedition look equipment but the weight way up high, the addition of an aerodynamic brick onto an already aero challenged truck, lack of storage after use (thinking about leaving it mounted full time but decided against that due to parking garages then not being an option) and the fact that it will be snagged, rubbed and hit by branches, etc... This leaves me with a ground tent.
For sheer comfort and weather protection year round I love my Montana Canvas spike 2. http://montanacanvas.com/spike-tents.phpvas These tents along with a small wood stove, cots, roll up table and chairs weight less then most of the smallest roof top tents and are luxurious for two. We have rode out winter blizzards and summer monsoons with equal satisfaction. The wood stove is sure comfort and provides a great cook stove as well as a hot water jacket at under 20 pounds. We can have the tent up and smoke coming out the chimney in under 15 minutes. It works fine in the canoe or with the horses but it's no backpacking tent.
Its not that I am abandoning the RTT, but I went this route because its what fit the budget and we were both very happy. After we loaded up from the first night, we just collapsed the tent and left it "ready to be rolled out" at the back of the truck. When we made it to the second campsite, we just unloaded the tent, set it up and then unloaded the truck contents into the tent. The weight of the bins hold the tent down. The dogs slept in the tent area, and we slept in the back of the truck on an inflatable mattress( I am not a fan of these btw).