never heard of Rovan. that makes me doubt they would have good support. i do know the Losi DBXL seems to be the "go to" 1/5 scale for bashers and people new to 1/5 scale. they do cost $1400 though... but they are well supported and do have a healthy aftermarket.
the only other 1/5 i know anything about is the Redcat Rampage MT. it's a monster truck with independent suspension. i think it's about $900. and Redcat does have US support.