Custom role is unable to see the Accounts fields like COGS Account, Income Account, etc. under the Accounting tab of the Item record even if the using standard item form. The Administrator must add the Accounts permission to the role so the user can see those fields not only in the Item record but in other records as well.
1. Navigate to Setup > Users/Roles > Manage Roles.
2. Edit the role.
3. Permissions tab > Lists subtab > add Accounts with at least View access level.
4. Click Save.