In this work, the tensile property retention characteristics of high-performance glass and carbon rovings in warp-knitted reinforced fabrics and cement-based composites used in structural applications were investigated. Three types of warp-knitted fabrics, with differing stitch patterns, and cement-based composites were produced. The tensile strength retention and Young’s modulus retention of the roving in these fabrics and their influence on the properties of cement-based composites were compared on the basis of the stitch type. Samples of warp-knitted fabrics composed of glass fibres and carbon fibres exhibit retention of 76–87% and 65–87.6%, respectively, of the initial strength of the rovings. The highest Young’s modulus retention (~80%) occurs in the case of the fabric sample composed of glass rovings. The retention of the Young’s modulus in the fabric samples composed of carbon rovings was 37–60%. In addition, the translation of strength from the roving to the fabric and retention of the Young’s modulus in the carbon rovings decreased with increasing strength and modulus, respectively, of the original roving. On the basis of the data presented, we provided guidelines for the possible application of the developed fabrics. As conclusion, it is possible to reduce the cost of the raw materials by using fabrics whose original rovings have low tensile strength and Young’s modulus, but high retention properties.