  The superfluid density and superconducting gaps of superconducting
RbFe_{2}As_{2} have been determined as a function of temperature, magnetic
field and hydrostatic pressure by susceptibility and muon-spin spectroscopy
measurements. From the data, fundamental microscopic parameters of the
superconducting state like the London penetration depth \lambda, the gap values
\Delta, the upper critical field B_{c2}, and the Ginzburg-Landau parameter
\kappa have been obtained. In accordance with earlier measurements the ratio of
the superfluid density n_{s} \propto \lambda^{-2} to the superconducting
transition temperature T_{c}=2.52(2) K at ambient pressure is found to be much
larger in the strongly hole-overdoped RbFe_{2}As_2 than in high-T_{c} Fe-based
and other unconventional superconductors. As a function of pressure T_{c}
strongly decreases with a rate of dT_{c}/dp = -1.32 K/GPa, i.e. it is reduced
by 52 % at p = 1 GPa. The temperature dependence of n_{s} is best described by
a two gap s-wave model with both superconducting gaps being decreased by
hydrostatic pressure until smaller gap completely disappears at p = 1 GPa.
