Gravitationally lensed quasars in the reionization era: the prospective for the Roman Telescope

High-redshift quasars trace the extreme phases of SMBH and galaxy evolution at cosmic dawn. They are hosted by the most massive galaxies at their redshifts and harbor colossal SMBHs (with M_BH >~ 10^9 M_sun). With the help of lensing magnification, high-redshift gravitationally lensed quasars offer the best opportunity to conduct in-depth studies of high-redshift SMBHs and their host galaxies. However, our knowledge regarding lensed quasars at z>5 remains highly restricted due to the limited depth and sky coverage of current sky surveys. The upcoming sky surveys (like Euclid, LSST, and Roman) are expected to produce the first large sample (>~50 at z>5.5) of lensed quasars in the reionization era. In particular, the spectroscopic capacity of Roman makes it the most promising mission for building a complete sample of high-redshift lensed quasars. These lensed quasars will be valuable objects for follow-up observations using JWST and ALMA, enabling crucial experiments not feasible with non-lensed quasars. Specifically, these lensed quasars will allow us to accurately measure the quasar luminosity function, explore the faint end of high-redshift quasars, and characterize the small-scale structures (down to ~50 pc) of the quasar host galaxies