When you first start the roof command the option bar should show up with “Defines Slope” and you can check it or keep it unchecked and define after you draw.
If you don’t not check “Defines Slope” at the beginning of the roof command its ok. You can draw the roof and then select on the individual lines and click the check box from the Option bar to “Define Slope”.
Now you will see the triangle and you can click on it to change the slope or you can select on the line and change the slope in Properties.
What happens if you create your roof and you forgot to define your slopes? Simply click on the roof and from the ribbon click on “Edit Footprint” then you can select each line and from the Option bar you can check “Defines Slope” and modify the slope.
Now one more thing;
I have customers who do not want to use degrees for their slopes so here is how you can change this;
From your ribbon go to the Manage tab.
Click on Project Units.
From within the Project Units dialog box click on the Format button for Slope. The Format dialog box will open and you can change how the slope units are shown. Click the OK button in both dialog boxes to get back to your drawing.
Now when I click on the roof line to edit it my slope units are changed.