i'm taking part in a 25 mph or 40 kph roll race event, and was wondering if there is anything i can do to prepare like a certain approach in tuning or something mechanical.

 

Practice brake boost

 

Maybe not too much though lol.

OP: Fresh oil and make sure the car is up to par mechanically. Other then that, you should be good to go. Depending on how fast you're going up to, you may want to ensure you're on the conservative side with how much boost you're putting through the motor.

I'm just speaking in generalities as I have no idea about your set up or how aggressive your tune is.

 

How long is race? 1/4 mile? 1/2? 1 mile?

 

A question like this may be better suited for the drag racing section.