  We investigate the monopole excitations of the soliton in the
Nambu--Jona--Lasinio model. By studying the solutions to the corresponding
Bethe--Salpeter equation in the background of the soliton we exclude the
existence of real large amplitude fluctuations. This allows us to treat the
collective coordinate for the monopole excitations, which parametrizes the
extension of the soliton, in the harmonic approximation. The canonical
quantization of this coordinate yields a spectrum which agrees reasonably well
with the empirical data for the Roper resonance, N(1440), and the corresponding
one for the Delta, $\Delta$(1600). We also comment on going beyond the harmonic
approximation.
