Can Warlocks do rituals?
Since Warlocks aren't typically into the long hours of study required to learn and perform rituals, they tend not to be ritual casters. The classes that gain it right away are the Wizard, Invoker, Druid, Bard, Psion, Cleric, and Artificer. You could learn to cast rituals by taking the Ritual Caster feat, or through, I believe, some multiclassing feats.
--pseudo-edit--
Ah, found it:
Learned Spellcaster [Multiclass Wizard]
Prerequisite: Int 13, Wis 13
Benefit: You gain training in the Arcana skill, the Nature skill, or the Religion skill. You gain the wizard’s Ritual Casting class feature. In addition, you can wield wizard implements.
So, if you want to cast rituals and gain access to the Orb and Staff implements, that's not a bad feat to take. Also frees up one of your class skills for something else other than Arcana. If you decided to take this as your level 2 (or later) feat, you could retrain your class skills to replace Arcana (which you gain training in from the feat), so it's not a big deal to take this later, either.
However, since you don't have a 13 in Wis, you can always just take the Ritual Caster feat if you want. I've never personally found rituals to be that imperative to have, though they can certainly have their uses.
