Welcome to the forum. My wife and I just recently ordered a T21QBHW which appears to be the Flagstaff version of the Rockwood you are considering. We have had pop ups, hybrids and "conventional" travel trailers in the past. After all those we decided the T21QBHW is the "right size" for the two of us to start RVing again.
We wanted to avoid having another "soft side" pop up, or hybrid, with canvas due to the high humidity in the Southeast. Invariably it always seemed to rain on our last day out so we had to "dry out" the trailer before taking it back to the storage facility. That can be a real pain as our covenants do not allow RVs to be set up at home. The "hard side" eliminates the majority of those issues. Add in how much faster and easier it is to set up and tear down a "hard side" and the T21 was an easy choice.
I have only seen a few Chalet or Aliners and had written them off as they were too small, especially the bunks, and too expensive for our tastes. I do like the dormers and some other features they offer though. As far as quality goes we have owned other Forest River products and did not have any quality issues.
Since our T21QBHW won't be delivered until around 1 April I can't comment too much on your space concerns. However, last week my wife and I spent about an hour in the display model at our local dealer figuring out if it was right for us and how to load it and we didn't feel cramped. (The nice thing about being retired is we can go on a weekday when a long look isn't a problem for the dealership.
) After comparing the T19QBHW and T21QBHW side by side the extra two feet of "box space" really do make a major difference in how "big" and comfortable the trailer felt to us. I don't foresee any trailer claustrophobia outbreaks with the T21...
And for only a whooping $500 price difference we would be crazy not to go for the T21.