(Greater) Invisibility grants a lot of benefits, but it does have limits.
You can just guess the square
Even if you haven't pinpointed the exact location of your target, you can just guess and hit a square that you think your enemy might be in:
If a character tries to attack an invisible creature whose location he has not pinpointed, have the player choose the space where the character will direct the attack. If the invisible creature is there, conduct the attack normally. If the enemy's not there, roll the miss chance as if it were there and tell him that the character has missed, regardless of the result. That way the player doesn't know whether the attack missed because the enemy's not there or because you successfully rolled the miss chance.
Finding invisible creatures in combat
Even without any magic support, such as see invisibility, glitterdust or invisibility purge, pinpointing the location of an invisible creature is not too hard.
Note that once the rogue's location was pinpointed by a creature, yelling out his location, e.g. "Directly in front of me"/"He just stabbed my ankle" to his friends as a free action, making it easier for the others to "guess" his location correctly.
A creature can generally notice the presence of an active invisible creature within 30 feet with a DC 20 Perception check. The observer gains a hunch that “something's there” but can't see it or target it accurately with an attack. It's practically impossible (+20 DC) to pinpoint an invisible creature's location with a Perception check.
|Invisible creature is...
||Perception DC Modifier
|In combat or speaking
Pinpointing an invisible creature using perception is a DC 40 perception check, which is quite high indeed. However, the DC is lowered by 20 if the creature is in combat, such as your rogue.
Your stone giants have a perception modifier of +12. They can attempt the DC 20 perception check as a move action and then try to smack the rogue with their greatclub (at 50% miss chance) as their standard action, and yell out his location "Directly in front of me" to his friends as a free action.
Should that fail, you can always resort to groping around, checking two squares as a standard action:
A creature can grope about to find an invisible creature. A character can make a touch attack with his hands or a weapon into two adjacent 5-foot squares using a standard action. If an invisible target is in the designated area, there is a 50% miss chance on the touch attack. If successful, the groping character deals no damage but has successfully pinpointed the invisible creature's current location. [...]