So I have a question about the Sorcerer's Robe. Here is the text of it, "This dapper robe enables a sorcerer to add the effects of her 1st-level bloodline power to spells she casts. As a swift action before casting a spell, the wearer expends one use of her 1st-level bloodline power and selects one target of the spell to be affected by that bloodline power. If the spell allows a saving throw, a successful save against the spell means the bloodline power deals half damage (if it normally deals hit point damage) or is negated (if it does not). The robe can be used up to three times per day."
Now my question is with my bloodline power being a ray do I still need to make the attack roll if I was to use it with a spell that will always hit like magic missile?