The Nancy Grace Roman Space Telescope (Roman) will provide an enormous number of microlensing light curves with much better photometric precision than ongoing ground-based observations. Such light curves will enable us to observe high-order microlensing effects that have been previously difficult to detect. In this talk, we investigate Roman's potential to detect and characterize short-period planets and brown dwarfs in the source systems using the orbital motion of source stars, the so-called xallarap effect. We show that the Roman Galactic Exoplanet Survey (RGES) can detect warm Jupiters with masses down to about 0.5 Jupiter-mass and orbital periods up to about 30 days. Assuming a planetary frequency nearby the solar system, we find Roman will detect 10 hot/warm Jupiters and 30 close-in brown dwarf companions in the Galactic bulge during the RGES. These detections are likely to be accompanied by the measurements of the companion's masses and orbital elements, which will aid in the study of the physical properties for the close-in planet and brown-dwarf populations in the Galactic bulge.