Heat, resurfacing, and uneven/wrong wheel lug nut torque are the common reasons for warped rotors. Resurfacing takes away the metal that could have help dissipate heat. Uneven torque allows the rotor to flex in the heating/cooling cycles of braking unevenly. Rapid, repeated heavy braking or even a sticking caliper would do it.
If the rotors are still above the minimum thickness, consider getting them resurfaced. About $10 each at the local NAPA service center. Clean and lubricate your caliper hardware. Make sure the caliper pins glide freely. Kragen has these little Permatex synthetic gel lub packs for $1 a piece. Normally maintenance one pack per axle is more than enough. But to clean well and lube I'd use one pack for each wheel.
OE is ceramic. But if the batch Toyota is trying to sell you comes from "NBK" then you should walk away or tell them to bring out the Akebonos, marked "AK". Nissins are OK too but they tend to glaze the rotors.
I would just buy Akebono ProAct with integrated shims from your local parts store. Do check
formatting link
for prices. Also see:
formatting link
I've also used Raybestos PG-Plus semi-metaliic. Excellent brake performance and fade resistence. But they are really dirty and do not last as long (about 50% compared to ceramics), that's why we go the ceramic route. Raybestos QS ceramics are also excellent and brake very well, but they are slightly dirtier than the Akebonos.
If you need to replace the rotors, consider Raybestos Vehicle Specific Metallurgy rotors. I've used their cheaper "red box" Asimco-GS (a.k.a. Raymold) noised-dampening rotors without problems.
If you use the vented rotors check with the pad manufacturers to make sure their ceramic pads can go on there. Raybestos has these, but the Stree Tech Series is probably not available yet for that year of Camry.