Typically, tires should be rotated every 5, 000, but people recommend that oil should be changed every three, but you can actually wait until 5,000 to change the oil and get the oil and tires done at the same time.
No you don't always need to rotate you tires. Just check for wear and tear. always make sure you check your tires air and keep them at ##psi levels. Tires should be rotated at the specified intervals and whenever uneven wear is notice.
It will vary depending on the manufacturers recommendation and how you drive. I think 3,000 is a good idea for aggressive driving or a lot of towing. This should help your tires last longer.