Creating a One-Dimensional Array for use with AddUsersToRoles Method

Dear All
I've created an Excel spreadsheet for my users to upload into my web application to bulk import  memberships and roles into the application. There are up to 4 different roles which users can be members of so I'm using AddUsersToRoles to add the user to one or more roles in one line of code like this:
r.AddUsersToRoles(usernames, CreateListOfRoles(Role1, Role2, Role3, Role4))
As this line of code expects a one-dimensional array of roles, I have created a function to take in the roles from my spreadsheet, add them into a one-dimensional array, and return that to the AddUsersToRoles method. The CreateListOfRoles function looks like this:

Function CreateListOfRoles(ByVal Role1 As String, ByVal Role2 As String, ByVal Role3 As String, ByVal Role4 As String) As Array Dim ar As New ArrayList 'If the role boxes a ...