The new species Roccella ramitumidula is described from a tropical dry forest in the Pacific Coast of Mexico. The new species is characterized by fertile thalli, saxicolous habit, irregularly swollen branches and erythrin and lecanoric acid as lichen products. It differs from R. decipiens by its narrower and longer ascospores, irregularly swollen branches, uneven surface, and smaller branches. Sequences of the genetic markers ITS, nuLSU and RPB2 from the new species were added to a phylogenetic tree based on four genetic markers that included all the Roccella species known for the Americas. The biogeography and ecology of the species is discussed. We reported R. gracilis for the first time for the state of Jalisco, Mexico.