Disclaimer, I've never worked in this field of astrophysics. However, intuitively, I would be skeptical of:
the habitablity of planets AROUND interglactic rogue STARS, and how those planets form
Because for rogue stars to end up in intergalactic space, they were presumably ejected from their galaxies. This then ceases to be very interesting because star formation within galaxies is relatively well-understood, and galaxy dynamics leading to a star being ejected is also relatively well-understood, and we have no reason to think that the habitability of stars which are ejected are likely to be different from stars that aren't ejected.
However: you really should check out the literature and discuss it with your supervisor. It won't be trivial, but it should be something that a person of your caliber can do. Go to Web of Science or Google Scholar and search for example for "intergalactic habitability". A quick try myself didn't find anything (which is good, since it indicates this could be something to write a thesis on), but did find this related paper. I quote the abstract:
Hypervelocity stars are unique among the stars in the galaxy for their extreme
velocities relative to the galactic center, in some cases achieving galactic escape
velocity. Dozens of hypervelocity star candidates have been identified so far. One
population includes B-type stars apparently ejected from the galactic core. A second
population has been identified within the plane of the galaxy with no single origin. As a fast-moving energy source, hypervelocity stars could be uniquely valuable property in the galaxy for advanced civilizations. Given their potential for transportation and exploration across the plane of the galaxy or to other galaxies, they could serve as prime objects for Search for Extraterrestrial Intelligence (SETI) searches or as long-duration transports for far-future human exploratory missions. In addition, some hypervelocity stars may be entering our galaxy from extragalactic sources, making them possible mechanisms by which intelligences in neighboring galaxies could be exploring ours.
It's then up to you to see if there's any reason these hypervelocity stars should be different from the ones that remain bound to our galaxy. For example, is the ejection process somehow correlated to whether the star is likely to have habitable planets? A priori the answer is "no" (per what I wrote above), but there could be. You won't know till you search the literature.
Then, after you have a reasonable sense of what's already in the literature, you can talk to your supervisor about the feasibility of the topic.