where 2 go 4 brunch in Rosslyn Va?
I don't know how well you know the area, but Rosslyn is in Arlington. So unless you have a specific reason to limit yourself to the tiny area known as Rosslyn, I'd expand your search to include other neighborhoods in Arlington, which is a tiny county -- nothing is more than 20 minutes away by car, if that.
It's also very easy to get into DC from Rosslyn for Sunday brunch.
Possible eats in Arlington or nearby Alexandria:
Bob & Edith's Diner
Not really brunch, but Kabob Palace in Crystal City is 24/7 and very tasty.
Candidly, there isn't much in Rosslyn. I recommend Liberty Tavern brunch, which is about 2 miles (2 metro stops) away. It's my favorite brunch in Arlington. I like to try several dishes when I dine and the buffet has several choices that are all well executed and use good ingredients.
There are also several good brunch options in Georgetown, but it's about a 1 mile walk and not metro accessible. It's a nice walk when the weather is good.