Since being taken over by Claudio Ranieri in November, AS Roma has slowly developed for the better. We probably wouldn't see AS Roma in the round of 16 if they were still managed by Ivan Juric, or the previous manager who also included club legend De Rossi. Athletic Bilbao is certainly not an easy opponent, but they are not more dominant than AS Roma either, I think they have equal strength. From the odds displayed, and may change again, AS Roma is slightly more favored, is natural since in the first leg they will act as the home.
I remember I really didn't like Ranieri's return because I thought it would be unsuccessful and he would get nothing but negativity, but to my surprise he was able to improve things. I agree that at the moment these two clubs are almost equally strong and this is reflected in the odds, if the first game had been in Bilbao, I think we would have seen exactly the same numbers, only in favor of Athletic.