Archimedes figured this trick out a long time ago. Place it in a measuring cup submerged in water to determine it's volume. Convert the volume to cm^3. Then weigh it, and covert to grams. Divide the weight by the volume to obtain the density. The density of steel is about 7.8 g/cm^3, while the density of titanium is about 4.5 g/cm^3. You don't have to be that accurate since the density of the two materials is so different.
Ok, after doing a little bit of research, here is what I found. On this site it lists the Titanium rotor, but when you read the description, it says:
Material: Alloy Rotor, Titanium Bolts
Also, I found this forum post that says they are probably not titanium rotors, but steel rotors with titanium bolts, which seems to fit well (well enough anyway) with the description in the store link above. Most likely what you have is a steel, or alloy (use the magnet test) rotor, with possibly titanium bolts. To test if the bolts are titanium, weight them in your hand against a steel bolt of similar size. The titanium bolt should be significantly lighter. Or you could use a magnet. But it's probably easier to just figure it out by feeling the weight then to go around searching for magnets.