We have been to all the water parks over the years including this one, the Rojales one is fairly small and not sure it's worth all the hassle and cost of hiring cars etc to get there there.
If you want a water park then the best is Aqualandia in Benidorm which has loads of rides for all ages plus a large wave pool. You can get Daves coaches trip, just google them, and they pick you up in GA , drop you at the door with ticket and then pick you up and take you home.
aqualandia is more expensive but cost out the entrance to Rojales plus costs of transport and compare to coach trip, also Aqualandia is a good day out and I would say Rojales is ok for an afternoon.
There is also a good one in Torrevieja but can't remember name but without cars you would need to bus or , hire car there.