Using Bogoliubov_de Gennes equations,we obtain the self_consistent equation in a ferromagnetic superconductor. Taking into account the rough interface scatterin g effects, within Bogoliubov_de Gennes equations and Furusaki_Tsukada formula we calculate the dc Josephson current in the double ferromagnet_superconductor tun nel junctions. It is found that dc Josephson currents in FS/I/FS are suppressed by the ferromagnetic exchange interaction for weak barrier strength and weak rou gh interface scattering strength. The only exception that the dc Josephson curre nts increase with the ferromagnetic exchange interaction occurs if all three con ditions are satisfied: at low temperature, for strong barrier strength or strong rough interface scattering strength, and in an antiparallel configuration.