In "Bridging The Gap" Rabbi Avi Fertig talks about false perceptions. He says that we have the roots of our middot (not to be confused with root middot). Also, we have roots of behaviour. What is the difference between them all?
I will take a stab at this and also have sent a note to Rabbi Fertig to ask him to weigh in on this question.
Firstly, I'm not sure what root middot are in terms of Rabbi Fertig's intention, but in Mussar there are certain middot that sit at the root of all other middot. For example, chesed (kindness) requires someone to be in a natural state of giving rather than taking. Rabbi Eliyahu Dessler writes in his Discourse on Lovingkindness that giving and taking sit at the root of the tree of middot. If you are in a state of spiritual giving then you go down one side of the middah tree and if you are in a state of spiritual taking then you go down the other side of the middah tree. The giving tree is preferred over the taking tree (which leads me to suggest that you look at The Giving Tree also by Shel Silverstein).
Second, behaviour is an outcome of many things, including our tendency to certain middot (the bechira point written about by Rav Dessler), or rather certain levels of certain middot. Our behaviour is also moderated by our perceptions of events and people - whether those perceptions are true or false. For example, if my anger middah is raging high all the time because that's my natural tendency, then my external behaviour may be somewhat aggressive or negative in some way. Someone cuts me off in traffic and my perception is that they are rude and I get angry. I then find out that they were rushing home to care for their child who fell and badly hurt themselves and my perception of who that parent was changes and my behaviour changes. My original perception of the parent was that they were rude, now I understand that they were likely distraught. I can change my perception and change my behaviour without changing where on the continuum I sit with my middah of anger. I may still be inclined to anger, but now I can control better how that inner energy gets directed outwardly.
I don't know if that helps or helps cloud things more, so I'll turn it over to Rabbi Fertig now.