Another thing to consider is how often does the rogue get a surprise round?
If you are playing a rogue with core-only feats, you need to earn your name. Move as far in front of the party (within range of their shadowy illumination) and always hide and move silently while exploring. Put ranks in spot and listen so you get the jump on the enemy. Improved Initiative is helpful, but being able to listen at the door to be aware of enemies on the other side is extremely important.
Assuming a 16 dex and 10 wisdom, at 7th level very few opponents are going to spot or hear a +13, and very few are going to hide or move silently against a +10. With bow in hand open the dungeon door and get the drop on the orcs in the next room, win initiative, shoot again and then retreat. You are a better ranged fighter than a front line fighter anyway, and with a +1 shortbow he'll be able to easily hit the majority of flat-footed, no cover or melee (surprising them) CR 7 opponents with his +9 to hit. He'll deal two shots at 1d6+4d6 sneak, for an average of 35 points of damage before the enemy even gets to react. If he's smart he'll drop the weakest opponent (maybe the wizard).
What should he do during combat? The most useful ability? You can ready an attack against a spellcaster with the trigger "if she starts casting a spell." Casters prefer to avoid melee, so the shot shouldn't be impossible to hit. And a DC 13 (on average) concentration check may not sound to hard to beat, but many CR 7 casters aren't going to have +13. When the enemy wizard botches his check and loses the fireball spell everyone will thank the rogue. As an added bonus, the enemy wizard may draw his attention to the rogue and waste a reflex DC based spell on him too.
Are there ever any opportunities to sneak up and kill a lone guard who would alert the rest of the dungeon of the party's presence? This is another iconic role for the rogue, and it's an essential part of designing a balanced challenge for the party.
Also, is the DM awarding XP for disarming traps? And how often are you finding traps? Or secret rooms with hidden treasure? In one of our campaigns I give out xp for every room fully explored and every trap disarmed. The rogue may not be the most effective player in combat, but he should be the most useful outside of combat. He hogs up the spotlight at least 1/4 of the time, and when he does it he does it alone (again earning his name).
If the DM always surprises the party, never places lone guards and puts in few (and unrewarding) traps then the rogue will appear to be useless.
As for asking for help from the rest of the party during combat, here are some suggestions:
-Ask the fighter to grapple an opponent
-Ask the cleric or bard to bless you (or some other buff)
-Ask the wizard to cast invisibility and/or silence on you
You can also Use a Magic Device to cast buff spells on yourself (a 10 charge wand of invisibility and/or silence should last a long time for only 180 gp per usage vs 600 gp using potions).
Also, the wizard and fighter do not have diplomacy as a class skill, and even the cleric (with few points to spare for diplomacy anyway) doesn't have bluff, sense motive, gather info or knowledge (local), so is the rogue getting his fair share of opportunities outside of the dungeon?