Once you receive your final video from Rolla, you can download it to your Camera Roll from directly inside the Rolla app.
Go to the Videos tab
Tap on the project you want to share
Scroll to the asset type you want to share
Tap the "Download & Share" button
Tap "Download"
Once you see the confirmation that its in your Camera Roll, head to the Photos App
In your Recents folder, you will see the final video.