Definitely nearly the best way to go about it. The best way is to try to pass the buck to someone else.... if you can't then Marina's post is spot on.Hi,
In the first sentence, you might want to replace "rough" by "initial" (my choice) or "brief", but I wouldn't use "superficial" (negative connotation) or "not detailed" (incorrect).
On the other hand, I would definitely keep "rough estimate", which is a coined expression.
Hope this helps,