  An interesting possibility to ease the tension between various determinations
of |V_{ub}| is to allow a small right-handed contribution to the standard model
weak current. The present bounds on such a contribution are fairly weak. We
propose new ways to search for such a beyond standard model contribution in
semileptonic B -> rho ell nu decay. Generalized asymmetries in one, two, or
three angular variables are introduced as discriminators, which do not require
an unbinned analysis of the fully differential distribution, and a detailed
study of the corresponding theoretical uncertainties is performed. A discussion
on how binned measurements can access all the angular information follows,
which may be useful in both B -> rho ell nu and B -> K^* ell^+ ell^-, and
possibly essential in the former decay due to backgrounds. The achievable
sensitivity from the available BaBar and Belle data sets is explored, as well
as from the anticipated 50 ab^{-1} Belle II data.
