Database Table Desing Question

I want to design my little e-commerce project database. I am using ASP.NET
and Role based authorization.

I have 2 types of customers:
1)On-line customers
2)Walk-in customers processed by employee.
I come up with these tables so far:
1)Customers -- Collects cust info
2)Employees -- Collects emp info
3)Roles -- Role Info
4)EmployeeRoles
5)Orders

-- Online customers are processed by a default employee designated for that purpose.

-- Walk-in customers are processed under the servent's role ( the employee who process their orders).

-- tables customers & employees contain the same data can I merge them into on table "Users"?

-- My problem with this is Orders contain OrderID, CustomerID, EmployeeID.

Thanks in advance for your help.
Jamal.