Decision boundary
One role prepares the conversation. The other prepares the setup trail.
Sales development support helps an owner prepare for prospect work. Customer onboarding support helps an owner keep an approved customer setup path current. Neither role should decide qualification, pricing, contracts, access, configuration, scope, or customer commitments.
Put this in the first role brief.
"Use the approved source to prepare the named prospect-preparation or onboarding record. Hold and route any request involving qualification, targeting, consent, outreach approval, pricing, terms, a contract, scope, timing, access, configuration, a customer commitment, or a final completion decision. Link the source, note what is blocked, and name the owner who decides."