Thank you for your post.
I would recommend to do one of two things to get the result you're after, which I've put below.
1. Create a material in either of the roof tools then apply it to face or component/group that you've created. The link below will take you to a webinar we recently had which explains how to do this. Please note you will register to view the video.https://attendee.gotowebinar.com/register/6198001302739692547
2. Use the BIM Tool to add the geometry and associated information since you already know the area of the panels. With this option you can set an overall price for the panels.
Would you be able to please let me know if either of these work for you?