We consider Fourier multiplier systems on R-n with components belonging to the standard Hormander class S-1,0(m) (R-n), but with limited regularity. Using a notion of parameter-ellipticity with respect to a subsector lambda & SUB;C (introduced by Denk, Saal, and Seiler) we show the generation of both C-& INFIN; semigroups and analytic semigroups (in a particular case) on the Sobolev spaces W-p(k & nbsp;)(R-n,C-q) with k & ISIN;N-0, 1 & LE;p <& INFIN; and q & ISIN;N. For the proofs, we modify and improve a crucial estimate from Denk, Saal and Seiler, on the inverse matrix of the symbol (see Lemma 2). As examples, we apply the theory to solve the heat equation, a linear thermoelastic plate equation, a structurally damped plate equation, and a generalized plate equation, all in the whole space, in the frame of Sobolev spaces.