The rotational molding technology is becoming more popular and even outstanding some of the conventional polymer processing technologies. The production of polymer composites via this technology is still not described thoroughly. This work discusses the possibilities of obtaining polyethylene composites reinforced with short basalt fibers. Two methods of incorporating the fibrous fillers, dry-blending and through preliminary extrusion, are concerned. The application of the extrusion step to mixed polymer matrix with basalt fiber results in better distribution of basalt fibers than the direct dry blending polymer powder with fiber in the mold. The basalt fibers from rotomolded samples prepared from melt mixed plastic powder significantly reduced their length, leading to a substantial limitation in their reinforcing effect on the polymer matrix. The possible reinforcing effect was evaluated in a mechanical test such as a tensile test, impact test, and hardness. Optical microscopy helped in the investigation of the distribution of basalt fibers. Not only the physical structure of composites was examined, but also the chemical composition using the Fourier transform infrared spectroscopy. The spectroscopic analysis confirms a properly realized technological process without degradation caused by rotational molding or additional melt blending. The production of good-quality rotomolded composites reinforced with basalt fibers depends on the method of incorporating the fibrous filler.