SQL Scalar Function

CREATE FUNCTION [dbo].[Get_Full_RollName](@Role nvarchar(2))
RETURNS NVARCHAR(50)
AS
BEGIN
    DECLARE @type nvarchar(2);
    SELECT @type=(SELECT CASE UPPER(nvcRoleName)
                            WHEN 'SP' THEN 'SALES'
                             WHEN 'TC' THEN 'TECHINICIAN'
                            ELSE 'USER'
                        END
    FROM RoleMaster)
    RETURN @type
END