How tall do you have to be to ride the roller coasters?

It varies depending on the coaster. Their website and app both tell you the heigh requirements for each ride.

Each roller coaster in the park varies on the intensity. On "Kid-Sized Thrills", you have to be about 40" to ride alone, no minimum to ride with an adult. On "Moderate Thrills", you have to be about 40" to ride with an adult, and 48" to ride alone. There is a maximum height of 76". Finally, on "Maximum Thrills", the minimum to ride in general is about 52", and there is no set maximum.