To overcome texture and flavor challenges in fermented plant-based product development, the potential of microorganisms is generating great interest in the food industry. This study examines the effect of Lactobacillus rhamnosus on physicochemical properties of fermented soy, oat, and coconut. L. rhamnosus was combined with different lactic acid bacteria strains and Bifidobacterium. Acidification, titratable acidity, and viability of L. rhamnosus and Bifidobacterium were evaluated. Oscillation and flow tests were performed to characterize rheological properties of fermented samples. Targeted and untargeted volatile organic compounds in fermented samples were assessed, and sensory evaluation with a trained panel was conducted. L. rhamnosus reduced fermentation time in soy, oat, and coconut. L. rhamnosus and Bifidobacterium grew in all fermented raw materials above 107 CFU/g. No significant effect on rheological behavior was observed when L. rhamnosus was present in fermented samples. Acetoin levels increased and acetaldehyde content decreased in the presence of L. rhamnosus in all three bases. Diacetyl levels increased in fermented oat and coconut samples when L. rhamnosus was combined with a starter culture containing Streptococcus thermophilus and with another starter culture containing S. thermophilus, L. bulgaricus and Bifidobacterium. In all fermented oat samples, L. rhamnosus significantly enhanced fermented flavor notes, such as sourness, lemon, and fruity taste, which in turn led to reduced perception of base-related attributes. In fermented coconut samples, gel firmness perception was significantly improved with L. rhamnosus. The findings suggest that L. rhamnosus can improve fermentation time and sensory perception of fermented plant-based products.