It depends. First of all you need to be sure that your judgment of “being messy” is correct. Assuming it is, there are two main points to keep in mind before being critical.
The Chazon Ish (Rabbi Avraham Yishaya Karelitz, a great 20th century Torah scholar) taught that the intention of the criticism must be for correcting the other’s behavior and not for any personal “pleasure”.
He writes: “There are some deeds that fall clearly into the category of good or evil. For instance, is someone maliciously hits another person, the action is clearly wrong. Conversely, if someone feeds a starving person, the deed is clearly good. But there are instances when the evaluation of a certain behavior as good or evil will depend not only on the action itself, but on the intention of the one who performed that action. Criticism and faultfinding fall into this category. If the faultfinder derives personal pleasure from his faultfinding, his action is evil. If, however, his sincere intention is to correct the mistakes of others and to help them grow, then his behavior is fitting and proper."
In addition the Chazon Ish adds that it is often better to remain silent than be critical and risk making things worse. Someone who had a tendency to constantly point out faults to other people asked the Chazon Ish "Is it forbidden to tell someone the truth?"
"It is definitely forbidden!" the Chazon Ish replied. "Except for special situations when it is forbidden to remain silent, we should not criticize others for their personality and mannerisms if they do not ask us for our opinion and we do not think that the person will actually do something to improve himself. Even when we feel the person will try to improve, we must be very careful not to tell him more that he will be able to accept and apply."
Based on the above I would suggest you evaluate your intentions to make sure they are “pure”, and also that you feel that your roommate will be cooperative and not resentful. If either of this conditions are not met and you find the current situation unbearable I suggest you consider finding a new roommate. Good luck.
