Wheel Care - Disc Rotors
To reduce weight, disc brake rotors for road bikes are thinner and thus more tender than thicker gravel and mtb rotors. When a wheel is removed, the rotor is exposed so, take care. Something as simple as a wheel falling over or being dropped is enough to slightly warp a rotor. The result of a warped rotor is an annoying rub that may straighten itself with the heat of brake application. More likely, the rotor needs to be straightened by hand or with a simple alignment tool. The good news is that brake pads float in the caliper so slight rubs are not hurting anything until they can be addressed.
To straighten a rotor at home or on the road, use a zip tie around the fork as a truing guide. There are specific rotor tools, but an adjustable wrench may also be used. Find the offending spot and gently press or bend the rotor back into place. More serious truing issues are best dealt with by your bike shop.