  In a recent Letter [T. Dornheim \textit{et al.}, Phys. Rev. Lett.
\textbf{121}, 255001 (2018)], it was predicted on the basis of \textit{ab
initio} quantum Monte Carlo simulations that, in a uniform electron gas, the
peak $\omega_0$ of the dynamic structure factor $S(q,\omega)$ exhibits an
unusual non-monotonic wave number dependence, where $d\omega_0/dq < 0$, at
intermediate $q$, under strong coupling conditions. This effect was
subsequently explained by the pair alignment of electrons %at an intermediate
range of wave numbers [T. Dornheim \textit{et al.}, Comm. Phys. \textbf{5}, 304
(2022)]. Here we predict that this non-monotonic dispersion resembling the
roton-type behavior known from superfluids should be observable in a dense,
partially ionized hydrogen plasma. Based on a combination of path integral
Monte Carlo simulations and linear response results for the density response
function, we present the approximate range of densities, temperatures and wave
numbers and make predictions for possible experimental observations.
