I am learning tongue trills as a singing warmup, which is basically just rolling your R's like in spanish for certain words. I am realizing that I have never been able to roll my R's. I also, interestingly, have noticed (when probing my mind for past experiences), that all people that have been able to roll their R's have had generally good facial development and those that could not, did not have great facial development. I for one cannot roll my R's.

In learning how to do this, I looked at some videos that basically say in order to do you this, you have to put your entire tongue on the roof of your mouth, while being able to vibrate the tip of your tongue, and making sure that your tongue fills all the way to the sides of your teeth. When I hear these words being thrown around, I immediately thought of mewing and that this could be a reason why some people just can't roll their R's. I certainly still cannot. I may have too narrow of a palate. They also stress how important it is to be able to relax your tongue for this to work. 

I am wondering if being able to roll your R's is a good indicator or having proper tongue placement for mewing, and if being able to relax your tongue on the roof of the mouth is also important to maintain is as a comfortable default posture. Just food for thought. Let me know if you guys can roll your R's and we can maybe have a little bit of an anecdotal poll.