You'll be fine. I towed a similar sized Rockwood Roo with a Nissan Frontier V6 CC 4x4 with no trouble. I definitely knew it was there when wind blew, but no issues. Moved up to a Titan V8 CC 4x4 and barely noticed it was even hooked up. Have since moved to a much larger TT.
The reason for the differences in TT GVWR might be the axle ratings and/or frame design. Since the Rockwood is an Ultralite it likely has aluminum framing that might limit its carrying ability. Although 942lbs does seem low for cargo capacity. The 2109s would give you another 150+lbs of cargo.
Also be aware of water weight if you plan to carry water in the tanks. That will eat a huge chunk of your load capacity.
