This page of the FF 7 Remake guide contains a description of the fight against Roche. He challenges you during Chapter 4 Mad Dash.
Roche is a member of the elite SOLDIER group and is a much more powerful enemy than the regular soldiers. You fight him first while riding a motorcycle, and then you have a classic 1 vs 1 duel.
The enemy has 8,160 HP and is weak to fire. If you are equipped with Fire Materia, you can easily attack him with this element, though it is better to save MP on Cure. The enemy doesn't have much resistance to physical attacks, so it is best to focus on this fighting style.
Use Punisher Mode to block and counter his attacks. When you take half his life, he will use Ignition Flame attack - avoid it by rolling sideways. Roche is quite slow and moves lethargically after attacks, so use this to opportunity to attack him with your sword.
After defeating the enemy, you will receive Elixir.