[SalesForce] Lead assignment round robin based on lead source

You could keep track of each group by custom settings. This implies you'll need some apex code to determine the next value to use.

Start with a custom list setting. It should have one custom field, a number. The name value will be some specific value for each queue, say East or West.

Then, you have a trigger, before insert. Have the trigger determine if each lead will go East or West. Copy the value from the appropriate custom setting to a custom field that is hidden from users, and increment the value afterwards.

The assignment rules can be built the way they are today, using the custom field value and the East or West designation, as appropriate.

Other alternatives are available, as well, such as an asynchronous call after creation to reassign the leads afterwards. The trick is the custom setting, to track which user is next in line for the round robin assignment.

You can look for the options to use Omni-Channel for lead assignment.

Use Omni-Channel to create work items from Salesforce records and route them to the most qualified, available agents in your organization. That’s right: You can automatically route most Salesforce objects in a Salesforce Queue—including cases, leads, chats, and SOS video calls—to your agents.

With Omni-Channel, you can set the priority of work items to make sure that critical assignments get taken care of quickly. You can manage your agents’ capacity and availability for work to ensure that they’re given only the number of assignments that they can handle. You can also define which agents can work on different types of assignments. Best of all, agents no longer have to pick and choose work items manually from a queue, and managers no longer have to triage or dispatch work to agents. Work is served to the most qualified available agent in real time!

For more information, refer Push Work to Qualified, Available Support Agents with Omni-Channel