Even vehicles equipped with hill assist feature may roll slightly if stopped on a gradual incline when you release the brake pedal. On steeper grades the hill assist feature does not necessarily give a beginner the time they need to set up the clutch and gas pedals to prevent rolling.
However, you can hold your vehicle momentarily on slight grades by releasing the clutch to the friction point before you release the brake pedal, giving you a temporary hold until you can rev the engine slightly. Once the engine is revving and the car is balanced in a stationary position, you can control the speed by modulating the clutch until you build enough speed to release it.
On steeper grades use the parking brake to secure the vehicle in position until you can momentarily hold the car still with the clutch and gas pedals. Release the handbrake, and you’re ready to go.