Communication between your Windows devices happens using Microsoft Project Rome APIs. You can read more about it at the Microsoft website.
Communication between Windows and Android devices happen using a combination of Project Rome APIs and Roamit's own servers.
Because of this, Roamit might send some of the data you are sharing to its servers, and then to Google's push notification services.
The shared data is removed from server as soon as it reaches Google notification service, and is not shared with any other third-parties.
When you activate 'Show my Android devices' option, your unique user id (retrieved from Microsoft) and some basic info about your devices get stored on Roamit's servers.
This data is necessary for Roamit to be able to identify you and your devices.
History of what you send and receive might get saved on your own devices, but not in the cloud.
Roamit may save and send anonymous data about app usage, to further improve the app. This data is just general information about how users use the app, and does not contain actual clipboard data, URLs or files of users, even anonymously.