If you're having difficulty trying to defeat 2-3 enemy robots, try this:

1) Use the 'Lock-on Camera' (press down on your D-pad) to target 1 of the enemies, but DO NOT attack him.

2) Run around to set that particular robot in the line of fire of the other ones. You'll notice that the robot is going to get hit by his own friends, but DON'T stay in the same location for long because the targeted enemy could still fire at you, so run around then go back to that location so he could get hit by his friends again. Do this until 1 robot is left.

3) Its easy to kill 1 robot, it only takes common sense. Just go behind him, then attack him. Don't let him turn around to face you, when he does, you'll just have to walk up to his back again. Try to attack him when you're using 'Spider Reflexes' that way you'll give off more damage.

Always remember don't attack 2 or 3 enemy robots head on because you are more likely to get hit by the missiles, and don't try to dodge the missiles for a long time because 1 of the missiles could land beside you and you'll get hit by the area effect damage by the missiles.

This is my way of killing the robots. If you know an EASIER way, then by all means do it.