B112 requires with Area Effect.
It says "incompatible with Melee Attack and ranged attack modifiers"
- 82 for Telekinesis allows Emanation, even though the base range is only 10 yards instead of the 100 yards Emanation assumes from unmodified Innate Attack.
- it doesn't say to, but in cases like these, to take Emanation as a limitation should probably require taking Increased Range to get to 100 yards like an innate attack, for pricing balance
- same with inherently melee attacks enhanced to be Area Effect, so this isn't a net negative, they should probably need to take Ranged +40% first!
- 102 suggests GMs might allow Explosion to substitute for AE requirement.
- "The GM may allow Emanation in conjunction with Explosion (p. B104) instead of Area Effect. Use this combination to simulate antipersonnel grenades mounted on the hull of an armored vehicle . . . or the attack of an entity that flares like a phoenix without destroying itself."
- 165 defines what is included
- Ordinarily ranged attacks modified with Emanation,
- advantages such as Obscure and Mana Damper (Switchable),
- and similar zero-range area-effect abilities.
- page 20 gives an example of combining it with Malediction and Selective Area
- page 26 gives example of combining with Bombardment
- Emanation never requires an attack roll. You only bother rolling if your attack is dependent upon your margin of success (e.g., it's a Malediction) -- and even then, if you fail the roll, you're still considered to have succeeded with a margin of 0. (This last rule is a general-case one for any situation where you're guaranteed success but must still roll to determine your margin of success.)
- Emanation obviates the need for an attack roll. It's one of its built-in benefits, implied heavily in the Basic Set but then made more explicit elsewhere. Aura is similar in this way, just longer-lasting.
- Otherwise, whether attacking the ground you're standing on with an area effect requires an attack roll is up to the GM. There are about a million different variations on how this could go down, so use common sense. If the attack could feasibly miss, then ask for an attack roll -- though speaking as GM I'd give both the usual +4 for attacking an area and a +2 circumstance bonus for "shooting straight down" (a.k.a. the Inverted Takedown bonus for those of you who play Arkham: Batman games).
- No roll to hit is required – that's the official answer, and PK has already given it.
- As to why Emanation is still a limitation, that has to do with the lack of range and the requirement to buy Area Effect. The true cost of Emanation is in fact +30% because it always comes with Area Effect, 2 yards, +50% at a minimum . . . and if you want to not fry friends, you'll need Selective Area, +20% as well, for a net +50%. For the same +50%, you could affect any two-yard-radius area you like at Range 10/100. Yes, there would be risk of scatter, but you wouldn't have to stand next to people who could just punch you in the face.
The above shows the inherent assumption of the 10/100 stats. Things like Telekinesis or Leech don't have that!