Stryker is a weird combination of a zoner and aggressor.

Stay far away from your opponent and swap between gun and grenades. If the opponent tries to jump over your projectiles, hit them with a high grenade or an ex grenade and keep doing this.

If you're opponent starts to trade projectiles with you, wait until you are absolutely sure he is about to throw a projectile and use the roll toss. Unless they used a low projectile, you should roll under their projectile and get a free roll toss on them, and use EX roll toss to get across the screen and deal a good 16% worth of damage.

As for close up encounters, Stryker isn't too great. He has a combo that has a low hit in the middle, use this then cancel into roll toss. I'd tell you the inputs but i can't remember.

hope this helps a little at least.