If you do not have a 3.5 mm plug on your smartphone, you likely received a cable to convert from a 3.5 mm headset jack to the headset plug on your smartphone.
If you cannot find this converter cable, you have two options:
Option 1: Set up your Roost Smart Battery without the included speaker. At the step in the app where you see this screen, please tap "No" and continue to follow setup instructions in the Roost app.
Option 2: Set up your Roost Smart Battery with the included speaker that has a 3.5 mm jack. You will need to purchase a converter cable. Please consult information on your phone manufacturer's website before purchasing any converter cables. After you have a cable, you can tap "Yes" on the setup screen as show above and continue to follow setup instructions in the Roost app.