First set up your VAT and Taxes in WooCommerce > Settings > Tax.
Here is how net prices (ex. VAT) and tax exempt works in Roles & Rules B2B.
Select the roles you want to show with ex. VAT in the Roles with Net prices list. Active roles (set this in Roles & Rules B2B (General > Active (green icon shows it is active)) will now see prices with no VAT in the shop, when checkout VAT will be added on the order. (image below). Use the text after ex.VAT to show customers that the products is ex. VAT.
Roles with tax exempt is to use in combination with ex.VAT roles. When in use no taxes/VAT is added to the order (and in checkout).
Ex. VAT (net prices in shop)
No VAT and tax exempt
If you select roles with tax exempt your roles with net prices will get no VAT and Taxes on prices in the store and on checkout. See example ( image below ).
Tax exempt (no VAT and Taxes on orders)
Active roles
The green icon shows that the role is active and your rules will be applied in the shop. (Just check the active checkbox and save to make any role active)