The protocol will come into effect from next Monday.
Patients can be taken directly to Roscommon Hospital following agreement by the facility's management and the National Ambulance Service.
The hospital's A&E was closed in 2011, and this decision has been made following the ongoing pressure on emergency departments.
Certain patients who meet strict criteria will be taken to the model two facility between 9am and 3pm.
The same system is operating at Mallow General Hospital and in Ennis.
Roscommon Galway Deputy Denis Naughten says:
"While this won’t resolve the crisis in our local emergency departments, it will mean that patients will get access to more timely care which will allow them to be discharged from hospital far quicker.
This new protocol will be of particular benefit to older people who could end up spending up to 24 hours on a trolley in an emergency department. These patients can now be transferred directly to Roscommon Hospital by ambulance for medical care following consultation between the paramedic and the hospital consultant."