In this verse the pronoun "his" refers to the godless person, who represents godless people in general. It may be helpful to readers to use the plural pronouns "they" and "their." (See: [[rc://en/ta/man/jit/figs-genericnoun]])
These two phrases have similar meaning, but the meaning is unclear. Possible meanings are 1) he appears to be well-rooted in the rocks, taking advantage of every opening or 2) his roots cannot find fertile ground and must try to find nutrients among the rocks. (See: [[rc://en/ta/man/jit/figs-parallelism]] and [[rc://en/ta/man/jit/figs-metaphor]])