For the roller coaster rides in the parks, do they have cubbies or somewhere to put bags securely before going on the rides?

The lockers provided are somewhat small. I would recommend not bringing too much stuff.

All rides needing bag storage will have free lockers available before entering the waiting line.

The lockers are free

Yes

For rides that do not allow items on them, lockers are provided. You have a time limit based on the rides current wait time. So if a ride has a ninety minute wait time, you would have 2 hours of time to stow your stuff. There is a charge if you go over that time limit.

Yes they are mandatory for the coasters and free while you ride

How much do they usually cost?

Yes all over the parks

Yes they do... Also I think it is possible to rent our lockers to keep luggage/valuables