Once the game of rounds ends, there are only two options.
Return to lobby
OR
Ready Up (new matchmaking session)
Is it possible to force the game to start a new game of rounds with the current connected players, setting the round score back to zero?
Yes, you can have a single round game with no winning conditions set and use devices or verse/devices to make fake rounds.
Sometimes this is preferable,
at the moment some devices like prop manipulators, fail after the first round.
Also Spawnpads reset changed settings like enable/disable when the round ends (or they used to)
I thought it would be easier, without using verse 
Oh, I just reread your question… now I know what you mean.
I always assumed a game would repeat over and over until there were no players left…
Thats a bit of a worry.
What do you mean? A worry because it should repeat itself by default or a worry because you were surprised that it wasn’t implemented?
Maybe a bit of both, I’d like it to repeat itself by default, surprised it isn’t and now I’m wondering what the answer to your question would be, is there a way to make it repeat when players are still active ?
Giving players a direct choice to return to lobby instead of repeating games automatically is not good for retaining players.
Exactly, hopefully someone can help us with more insight.
There’s NO way for you to restart a game similarly to how you can in an edit session and reset the rounds to 0. In a normal play session once all the rounds are finished or game is finished they’ll be prompted to either re-ready up or back out to the lobby.
The closest thing you can do is “fake” the rounds and never end them but just respawn the players but thats really buggy
Can you clarify this? It cannot be done, or it can be done?
Respawning all players is fine as long as the majority of players remain! How can it be done?
You CAN’T reset the actual rounds of fortnite creative. You need to code your own “fake” rounds and respawn players using verse but thats complicated and can run into unexpected issues