  There is a degeneracy in the interior structure between a planet that has no
atmosphere and a small Fe content, and a planet that has a thin atmosphere and
a higher core mass fraction. We present a self-consistent interior-atmosphere
model to constrain the volatile mass fraction, surface pressure, and
temperature of rocky planets with water and CO$_{2}$ atmospheres. The
parameters obtained in our analysis can be used to predict observations in
emission spectroscopy and photometry with JWST, which can determine the
presence of an atmosphere and, if present, its composition. We coupled a 1D
interior model with a supercritical water layer to an atmospheric model. In
order to obtain the bolometric emission and Bond albedo for an atmosphere in
radiative-convective equilibrium, we used a low-resolution k-correlated model
within our retrieval of planetary mass, radius, and host stellar abundances. We
generated emission spectra with the same model at a higher resolution (R =
200-300). An adaptive Markov chain Monte Carlo was employed for an efficient
sampling of the parameter space at low volatile mass fractions. From our
interior structure retrieval, TRAPPIST-1 c is most likely to present a bare
surface, although the presence of an atmosphere cannot be ruled out. We
estimate a 1$\sigma$ confidence interval of the surface pressure for a
water-dominated atmosphere of $P_{surf} = 40 \pm 40$ bar. We generated spectra
for these two scenarios to compare with the emission flux of TRAPPIST-1 c
recently observed in the MIRI F1500W filter. This is compatible with bare rock
surfaces or a thin atmosphere with little or no CO$_{2}$. In the case of 55
Cancri e, a combined spectrum with NIRCam and MIRI LRS may present high
uncertainties at wavelengths between 3 and 3.7 $\mu$m. However, this does not
affect the identification of H$_{2}$O because it does not present spectral
features in this wavelength range.
