Contradiction with 1 Corinthians 8:2
This verse suggests that if anyone thinks they know something, they do not yet know as they ought to know, which contrasts with the confidence in one's guidance in Romans 2:19.
1 Corinthians 8:2: And if any man think that he knoweth any thing, he knoweth nothing yet as he ought to know.
Contradiction with James 3:1
This verse warns against many being teachers, implying a caution about self-assured guidance, contrary to the confidence of being a guide in Romans 2:19.
James 3:1: My brethren, be not many masters, knowing that we shall receive the greater condemnation. [condemnation: or, judgment]