Is a spell with an attack roll "an attack" for the purpose of Sneak Attack?

Question

Sneak Attack says:

When you attack a creature and hit, you can deal extra damage to that target if you have advantage against it or if another enemy of the target is within 5 feet of it and that enemy is able to take actions.

Emphasis mine. Now, suppose I am going to play a High Elf rogue, and select ray of frost as my racial cantrip. Since the ray's damage scales by level (unlike Rogue's standard physical damage progression, which is quite limited), I am thinking about Sneak Attacking with that spell, which nets into 8d6+5d8 plus 10-foot decrement of movement speed in the 20th level, if it's legal. Is this behavior correct? Are spells with attack rolls valid for making sneak attacks, like they were in 3.PF? If they do, does the added Sneak Attack damage assume the same damage type (e. g. cold for ray of frost) as the spell's damage type? Does allowing this give unfair advantage on my hypothetical High Elf rogue over other characters?

Answer 1

Sneak attack now specifies that you can not use spells, and must use a finesse or ranged weapon attack.

Sneak Attack ... The attack must use a finesse or a ranged weapon. (PHB5e p.96)

However, spell attacks are subject to critical hits and count as an attack just like a non-spell attack does. The main difference is that you don't add your spellcasting ability modifier to the damage unless you have some abililty or the spell specifies that it does.

Answer 2

How to Play document states "Actions in Combat" as following:

Attack

Whether you are swinging a sword, launching an arrow from a bow, or brawling with your fists, you are making an attack, the most common action to take in a battle. See “Attack Basics” below for the rules that govern attacks.

Cast a Spell

Many adventurers, such as mages and clerics, have access to spells and can use them to great effect in combat. A spell requires a single action to cast, unless noted otherwise. See the “Magic” section for rules on spellcasting.

(from How to Play document on the appendix of Ghost of the Dragonspear.)

Notice that "Attack" and "Cast a Spell" are listed in different entries, and are detailed in different sections. This implies that physical attacks and casting a spell fall into different realms. You are either "casting a spell", or "attacking", but not both.

Casting ray of frost is casting a spell, so it doesn't fall into the realm of physical attack. Thus, I don't think Sneak Attack damage can be applied to it, which requires you to make an attack.

Answer 3

While the playtest rules has not explictly stated that attacking spells are attacks, it seems to regard them so, which would be beneficial .

Regarding them as attacks means they enjoy critical hit, benefit from bardic performance and bless, can do coup de grace, can be interrupted like attacks (e.g. Shield spell), etc. More fun and more consistent.

And rules seems to assume that attack roll imply attack. For example see benefit of being hidden, if attack roll does not imply attack the rule would be broken, since you can do spell attack rolls with advantage without revealing yourself.

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That being said, if you are concerned with the damage, perhaps the problem of sneak attack lies in sneak attack not limited to weapon attacks like many other martial feats and martial features.

The damage is not that game breaking either, to be honest.

At 20 level an offense oriented fighter has at least 5 to 6 attacks (off hand, dancing sword, etc), each attack applying (multiplying) strength bonus, weapon bonus, class features, and damage buffs from friends.

Using +1 weapon, 20 Strength, 4 attacks as a baseline, that's (1[W]+6)*4 which is 4[W]+24, or around 7d6+4d8. Not far from 8d6+5d8.

Reality is more like 5[W]+50+5d8 and/or 5d12, plus maneuvers or superior critical. (4 attacks + offhand, +3 main weapon, 25 str, bardic inspiration d12 or crusader's mantle d8)

Since sneak attack and and cantrip can only be used once per turn, meaning all bonus damage only apply once, it can't compete at all.