You can choose to frame with rafters or trusses. You can also select the members you want to use and edit the precise dimensions of your roof’s framing configuration.
To edit a roof’s framing details:
Click on a roof edge to select the roof.
Right-click and select Properties, or select Edit > Modify Elements > Properties.
To select a member type for your rafters or trusses, click the Specify Framing button on the Basic page. In the Roof Framing dialog, click Select to select a member from the catalog, then specify the spacing between the members in the Spacing edit box. Click OK.
In the Roofs dialog, select the Support and Details tab.
Edit the parameters as desired.
Once you have set your properties, click OK.