No idea. (I am not the best at discerning. God gives it to me sometimes, but it is something I struggle with. lol) But I also don't see discerning as a gift talked about in Romans. Do they have to be connected? Ruling and teaching are included in that list in Romans 12, but I got squat abilities for either of those too. 
I really don't think everyone has to be gifted with every gift. (Toe, finger, mouth, ears again. All one body but different needed pieces to the body.) So, I'm really asking if discernment has to go with mercy, gift wise. (I see it's wise not to paint a rich man's house for free, simply because he'd like the free service. But it is merciful to fix a home of someone in such straits that the person needs it, but can't afford it. Might be that kind of discernment you mean.)
I really don't think everyone has to be gifted with every gift. (Toe, finger, mouth, ears again. All one body but different needed pieces to the body.) So, I'm really asking if discernment has to go with mercy, gift wise. (I see it's wise not to paint a rich man's house for free, simply because he'd like the free service. But it is merciful to fix a home of someone in such straits that the person needs it, but can't afford it. Might be that kind of discernment you mean.)
To another the working of miracles; to another prophecy; to another discerning of spirits; to another divers kinds of tongues; to another the interpretation of tongues: 1 Corinthians 12:10