So I believe I've seen the answer to this in the CRB before but I can't seem to find it. Anyway, I'm about to play in a game and my character has Combat Expertise, Improved Trip, and Improved Disarm and I was wondering if feats that affect your attack roll (such as Combat Experise) affect your CMB when you use them.
For instance, if I use Combat Expertise and I'm taking a -1 on attack rolls for a +1 to my AC, do I also take a -1 to my CMB?
Yes, because your CMB roll is an attack roll affected by things that affect your attack roll such as the enhancement bonuses from weapons, and the effects of spells, feats, abilities, etc. This means that combat expertise would affect your CMB rolls, and even things like a bardic performance.
The text for Combat Expertise says: You can choose to take a –1 penalty on melee attack rolls and combat maneuver checks to gain a +1 dodge bonus to your Armor Class.
so it's built into the feat.