Is there a way to assign deals automatically to sales reps?

Yes, Vtiger CRM's assignment rules - Round Robin and Least Loaded - will help you do this.
You can assign leads, contacts, and deals automatically using assignment rules.

Follow these steps to set up assignment rules:

1. Click your display picture located on the top right corner of the screen.
2. Click Settings.
3. Look for Automation and select Assignment Rules.
4. Pick a module you want to set up assignment rules for, from the Select Module drop-down.
5. Pick a user group to which you want to apply the rules.
6. Choose an assignment mode from Assignment Mode header.
7. Pick members from the group to which the rules must apply from Members header.

Your assignment set up is saved automatically and comes into effect.

Note: You can access Settings only if you are an Admin user.