I don't understand the question. Are you asking if it's possible to use the special notation like f(x) = x^2 for the creation of vector valued functions? If so, the answer is currently no, but it could probably be added to the Sage preparser without much problem. Of course you can always define the function rot the ordinary way to take a vector and return a vector:
sage: rot = lambda v: vector([1/v[0],1,1])