First soak it with penetrant. PB Blaster works great. While it's soaking in, go buy the kind of impact driver that looks like a screwdriver handle, you hit it with a hammer. Clean out the screw head really good so the bit fits GOOD.

If that doesn't work, use a drill. You don't really need that small bolt. The lug nuts hold the rotor on, the little bolt is only for assembly-line convenience.

If you get it off, use anti-seize so you can get it off next time.