I saw 2 holes in the rotor . Are they threaded ? If they are , I think I know what they are far .
If the rotor is rusted to the axle flange , apply penetrating oil in the holes and any other place it looks like it would help .
Take 2 bolts of the appropriate length , diameter & thread pitch . Screw them in snug . Tighten each one 1/4 - 1/2 turn at a time , alternating between . Continue to apply penetrating oil and tapping on the rotor with an appropriate hammer .
Make sure to tighten the two bolts evenly . They will slowly push the rotor away from the axle flange . The rotor may pop off , when it breaks away from the axle flange .
I would try a wire wheel on the rusty axle flange , before I applied the anti seize .
Remove the 2 bolts from the old rotor & use them on the other side , if necessary .
God bless
Wyr