First of all, lasers are a rather bad idea in my opinion. The only use I'd see for them would be long range, like sniper rifles or orbital laser cannons. The primary advantage is that you don't see them coming.
This leads me to extra-long range sniperbots that will probably be a hard counter to infantry. Have the thing auto-target opponents and the operator sinply push 'Fire' or something. It will obviously have to have some absurd range.
The hard counter for these would be armored units. Since there are probably going to be helmets for infantry due to that the lasers will need some serious punch, therefore you really should need to get some Juggernaut Armor, closer to a mobile bunker really. As for ammo for these monstrosities, I'm proposing explosives, homing missiles, a lot of guns, all the good stuff. I'll also think the part that should be armored the most would be the top, as to counteract artillery. The thing must have some good speed just in case however.
Artillery would be more like orbital space sats, and come in two varieties - the laser variant is more for precision strikes and actually doesn't suffer from ammo problems like the metal rod variant does. Simply drop a metal rod on the target. These satellites will probably be dirt cheap. And then there will be satellite-to-satellite satellites armed with lasers, probably, or missiles. In this case, have the laser variant also shoot anti-satellite lasers or something. Counter? Other satellites usually, and perhaps an stationary heat-seeking rocket launcher.
I am also predicting the end of the traditional human infantry. Instead, we will have drones or semi-sentient combatbots, armed with a variety of weapons and leaning more towards a zerg-rush style tactic. Anti-tank weapons, anti-air, anti-person or kamikaze, everything goes.
My pet peeve here really are humanoid robots tho, human size and all. It's impractical, but wayy more awesome than the rest here.