2014 Kia Sedona - Rolls back

when I stop my car at the top of steep uphill slope, it feels as if the minivan is rolling down, after the light turns green I have to press hard on the accelerator, which makes a loud noise, in order it shouldn’t roll back. any suggestions?

Some things that come to my mind:
Idle too low.
Faulty transmission pump
Low transmission fluid
Torque converter

You have to hold it in place with the brakes. Every car with an automatic transmission will roll backward when stopped going up a steep hill. It takes a lot more power to get it started uphill. It sounds like a normal thing.

The design of modern automatic transmissions is such that this phenomenon is normal, and the OP shouldn’t compare the functioning of this transmission to that of cars that he drove years ago.

DO NOT hold the vehicle in place on a slope by using the accelerator, unless you want to cause premature wear to the transmission’s clutches. Use the brake to hold it in place on a hill, and then accelerate when the light turns green.