Let G be a reductive affine algebraic group defined over a field k of characteristic zero. In this paper, we study the cotangent complex of the derived G-representation scheme DRep G (X) of a pointed connected topological space X. We use an (algebraic version of) unstable Adams spectral sequence relating the cotangent homology of DRep G (X) to the representation homology HR * (X, G) := π * O[DRep G (X)] to prove some vanishing theorems for groups and geometrically interesting spaces. Our examples include virtually free groups, Riemann surfaces, link complements in R 3 and generalized lens spaces. In particular, for any f.g. virtually free group Γ, we show that HR i (BΓ, G) = 0 for all i > 0. For a closed Riemann surface Σg of genus g ≥ 1, we have HR i (Σg, G) = 0 for all i > dim G. The sharp vanishing bounds for Σg depend actually on the genus: we conjecture that if g = 1, then HR i (Σg , G) = 0 for i > rank G, and if g ≥ 2, then HR i (Σg, G) = 0 for i > dim Z(G) , where Z(G) is the center of G. We prove these bounds locally on the smooth locus of the representation scheme Rep G [π 1 (Σg )] in the case of complex connected reductive groups. One important consequence of our results is the existence of a well-defined K-theoretic virtual fundamental class for DRep G (X) in the sense of Ciocan-Fontanine and Kapranov [12]. We give a new "Tor formula" for this class in terms of functor homology.