We don't offer a way for users to automatically upload their rosters into Sleeper. That's a feature we hope to offer in the future, but for now, there are other ways to go about getting your rosters entered.
The best and recommended way to do this is to use your league's actual draftboard and manually assign each individual player to their appropriate team.
You can learn how to move your league over by reviewing either of the following links:
Below, I'll explain how to enter rosters onto the draftboard.
View Your Draftboard
Press on the "Preview Your Draft Lobby" link.
Welcome to your draftboard!
Even though you're not about to have an actual draft, you're going to mimic one in order to get your players entered.
Make sure you do not actually begin the draft yet.
You will need to use each column for a specific team, so you'll have to keep track of which team is which.
Now, you can start assigning players to each team. Click on an individual tile and then choose the Set Player option.
Once you're done, your draftboard will look complete, something like this:
Once you have entered all of the players, you'll want to go to the settings icon in the top right and Begin Draft. This will allow the draft to start, but it will skip over any picks already filled in. The draft will immediately end and automatically assign these players to teams.
Invite Your Friends
Now that you have all of the rosters entered, you'll want to get all of your leaguemates into the league.
You can use the invite link on your league's homepage, or you can use the mobile app to invite them.
Your league's custom invite URL can be accessed via your league homepage and also in the league settings.
You can share this link with your friends through whichever means most convenient (i.e., email, text, social media), and the recipient of the link will automatically get dropped into the league!
If you need any help or want more specifics, you can read more on how to invite friends into your league.
Assign Users to Teams
At this point, you have all of your rosters ready to go, and all of your leaguemates in the league. Now, you just have to attach them to the proper roster.
Go to your league settings and click on Member Settings.
You'll see each of the teams listed with an option to add on the right of each. Click on that and assign the appropriate user to each team.
Once all of the teams are matched with their respective owners, your league is officially set up!