  Raman spectroscopy is frequently used to identify composition, structure and
layer thickness of 2D materials. Here, we describe an efficient
first-principles workflow for calculating resonant first-order Raman spectra of
solids within third-order perturbation theory employing a localized atomic
orbital basis set. The method is used to obtain the Raman spectra of 733
different monolayers selected from the computational 2D materials database
(C2DB). We benchmark the computational scheme against available experimental
data for 15 known monolayers. Furthermore, we propose an automatic procedure
for identifying a material based on an input experimental Raman spectrum and
illustrate it for the cases of MoS$_2$ (H-phase) and WTe$_2$
(T$^\prime$-phase). The Raman spectra of all materials at different excitation
frequencies and polarization configurations are freely available from the C2DB.
Our comprehensive and easily accessible library of \textit{ab initio} Raman
spectra should be valuable for both theoreticians and experimentalists in the
field of 2D materials
