Sure, via gravitational micro lensing. When the rogue planet or brown dwarf (which is not a planet) passes directly in front of a distant star (as viewed from Earth), the gravity of the rogue planet/brown dwarf will bend the starlight, focusing it towards Earth, causing the distant star to briefly increase in brightness. The amount of brightening depends on the mass of the body.
AstroBryGuy t1_ixxb99l wrote
Reply to comment by Alfred_The_Sartan in How would one calculate the gravity of a planet? by LoreCriticizer
Sure, via gravitational micro lensing. When the rogue planet or brown dwarf (which is not a planet) passes directly in front of a distant star (as viewed from Earth), the gravity of the rogue planet/brown dwarf will bend the starlight, focusing it towards Earth, causing the distant star to briefly increase in brightness. The amount of brightening depends on the mass of the body.
https://roman.gsfc.nasa.gov/exoplanets_microlensing.html