Use
VMS roles serve as a central control element in VMS. The roles are defined in Customizing, filled with data in the VMS basic data and then assigned to the user.
Prerequisites
You have created the VMS roles with key and description in Customizing (transaction OVELO19).

There are three types of role:
These are roles to which organizational data is assigned. Organizational data is dealer or importer data (plant, sales organization, distribution channel, division, SD document type, customer, ship-to party and payer). Roles for which the field Customer is filled with a value indicate a debtor, in other words a dealer.
The above fields are only evaluated in the web interface. If a dealer wants to create a sales order in the importer’s system via the web, the fields in the sales order are filled with the appropriate organizational data. The dealer cannot change this data.
The Customer field is also evaluated in the SAP graphical user interface (SAPGui). If there is an entry in this field, the customer/dealer that has been entered can only see the end customers that he/she has created him/herself but not end customers of another dealer. If the field is empty, all the end customers are visible.

If you work with the user parameters VELO_SOLDTO (customer, sold-to party), VELO_SHIPTO (ship-to party) and VELO_BILLING (bill-to party), you do not need to create a separate organizational role for each individual dealer. You only require one role for all your dealers. Each dealer is then identified by the user parameters as a specific dealer.
Furthermore, fields for the vehicle search area and original ordering party are assigned to the organizational roles. These fields are required in category management. The vehicle search area controls which users are allowed to see which vehicles during the search.
You can also assign a pricing procedure and a currency. These fields are required in the IPC. The prices in the IPC are displayed in the given currency and the pricing procedure overrides the pricing procedure that is contained within the IPC as a standard setting. The currency field controls the currency in which the user sees the prices in the vehicle overview and in the detail data for the vehicle.
The fields that affect purchasing are currently not evaluated and therefore have no significance. However, they can be included in customer-specific enhancements in BAdIs.
These are roles to which vehicle models are assigned. These roles specify which vehicles the user sees in the list of vehicle models.

You are an importer and want to see and manage all vehicle models; dealer X sells only small cars, dealer Y only motorcycles.
A vehicle model can be assigned to more than one vehicle model role.
These are roles that have been assigned to a configuration change profile (see also
Depending on the vehicle model, status and so on, the configuration roles specify which vehicle characteristics should be made visible for the user and which changes the user is allowed to make to the vehicle characteristics.
SAP advises you to create at least two configuration roles – one for you as importer and one for all your dealers (you, as importer are allowed to change more configurations than your dealers).
Activities
You should assign exactly one organizational role, one configuration role and one or more vehicle model roles to a user.

Use a role only ever in exactly one function. For example, only assign vehicle models to a vehicle model role and not organizational data. In this way, you achieve maximum flexibility when changes are made later.