A board-type or log-shaped cementitious siding system, or a cementitious roof shingle system, having a reinforcement material contained therein, and an optional foam insert at least partially enveloped by a cementitious shell. Each system is molded from cementitious slurry, including gypsum cement and a latex/water mixture. A reinforcement material and an amount of the slurry are introduced into an open molding system or an alternative closed molding system, either molding system including a mold surface member having a face defining an exposed surface of the siding or roof shingle system. The slurry introduced to the mold surface member is to a desired depth and/or weight, or for a desired period of time. A foam insert is optionally introduced into the molding system. After sufficient curing, the siding or roof shingle system is separated from the mold surface member and is ready for immediate use and/or further processing. Alternatively, a system and method are provided for continually producing board-type cementitious siding systems and cementitious roof shingle systems that may be elongate and can be cut to an appropriate size, without the need to produce individual siding or roof shingle systems of limited size. The cementitious siding and roof shingle systems continually produced thereby are ready for immediate use and/or further processing.