No, you don't always require an attack roll. Only some among aggressive spells require attack rolls. Attack roll is generally tied with touching the target (like chill touch you have mentioned) or firing a ray to the target (like disintegrate).
There are three kinds of criteria for determining the success of spell.
- Touch attack: You make an attack roll against the target's touch AC (hence the name "touch"), which disregards the enemy's AC bonus from armor. Usually targets a single creature.
- Saving throw: Target(s) designated or targets caught in your spell's area of effect must make a saving throw against the DC decided by the spell's level and your magic ability. For example, targets caught in the area of your fireball must make a reflex save against your spell's saving throw DC.
- No failure: Surprisingly, some spells don't allow chance to evade by either a missed attack roll or a successful saving throw. An example for this is power word kill, which always kills the target if it has less than 101 hit points.
Also, take note that there are spells which give benefits like bless, and they don't allow these kinds of saves ever.
P. S. To simplify the discussion, I didn't include spell resistance into the play. If the target has spell resistance, then "after passing a caster level check to affect the target" must precede wherever appropriate. Again, this only applies to spells that allow SR. (Detect Magic is an example of a spell that does not allow any of these methods of avoidance, so if you're using Invisibility, and someone scans your area with Detect Magic, they don't need an attack, you don't get a save or SR, and you will still be detected no matter how high your touch AC, save mods, or SR are.)
