Answer
Yes, it could "rise".
Work Step by Step
The rotating habitat creates the illusion of artificial gravity (see pages 147-149) because it is an accelerating reference frame.
Similar to the situation on Earth, the maximum air density is at the "bottom," near the outer rim of the habitat. The air density decreases as you approach the central axis of the cylinder.
A helium balloon will float from a region of greater air pressure to a region of lower air pressure, toward the center of the rotating habitat.
