We present a time-dependent analysis of CP violation in B-0->rho(+/-)pi(-/+) decays based on a 140 fb(-1) data sample collected at the Upsilon(4S) resonance with the Belle detector at KEKB. We obtain the charge asymmetry A(CP)(rho pi) = -0.16 +/- 0.10(stat)+/- 0.02(syst). An unbinned maximum-likelihood fit to the Delta t distributions yields C-rho pi = 0.25 +/- 0.17(stat)(-0.06)(+0.02)(syst), Delta C-rho pi = 0.38 +/- 0.18(stat)(-0.04)(+0.02)(syst), S-rho pi = -0.28 +/- 0.23(stat)(-0.08)(+0.10)(syst), and Delta S-rho pi = -0.30 +/- 0.24(stat)+/- 0.09(syst). The direct CP violation parameters for B ->rho(+)pi(-) and B ->rho(-)pi(+) decays are A(rho pi)(+) = -0.02 +/- 0.16(stat)(-0.02)(+0.05)(syst) and A(rho pi)(-+)= -0.53 +/- 0.29(stat)(-0.04)(+0.09)(syst).