First observations of the B-s(0) -> D-s*(-) pi(+), B-s(0) -> D-s(*)(-)s rho(+) and B-s(0) -> D-s*(-) rho(+) decays are reported together with measurements of their branching fractions. B(B-s(0) -> D-s*(-) pi(+)) = [2.4(-0.4)(+0.5)(stat) +/- 0.3(syst) +/- (0.4(f(s))] x 10(-3), B(B-s(0) -> D-s*(-) rho(+)) = [8.50(-1.2)(+1.3)(stat) +/- 1.1(syst) +/- 1.3(f(s))] x 10(-3) and B-s(0) -> D-s(*)(-)s rho(+) = [11.9(-2.0)(+2.2)(stat) +/- 1.7(syst) +/- 1.8(f(s)) x 10(-3) (f(s) = N-Bs(*)1 ((B) over bars(*)) / N b (b) over bar).
From helicity- angle distributions, we measured the longitudinal polarization fraction in B-s(0) -> D-s(*)(-)s rho(+) decays to be f(L)(B-s(0) -> D-s(*)(-)s rho(+)) = 1.05(-0.10)(+0.08)(stat)(-0.04)(+0.03)(syst). These results are based on a 23.6 fb(-1) data sample collected at the Y(5S) resonance with the Belle detector at the KEKB e(+)e(-) collider.