Summary: In your project's Sketch Scene, tap either the Apple Flyover or Google Streetview icon in the bottom right corner, zoom into the image, and tap the Pitch Icon in the upper left corner to bring up the RoofSnap Pitch Card.
To use Google Streetview to find the pitch:
1. Tap the far icon in the bottom right
2. Tap the street in front of the structure
3. Tap the icon in the top left corner
4. Move the digital pitch card to determine the pitch
The video tutorial below shows the same process using integrated Apple imagery instead of Streetview: