How do you vent a roof without soffit vents?

How do you vent a roof without soffit vents?
What do you do if your attic doesn’t have soffit vents and you are unable to add them?

Install low gable vents located above the top level of the attic ceiling insulation.
Use “eye-brow” vents that are on the top of the sloping roof surface near the soffit/eave area.
Focus on the other ventilation you have in the attic.

What do you do if your attic doesn’t have soffit vents and you are unable to add them?
  1. Install low gable vents located above the top level of the attic ceiling insulation.
  2. Use “eye-brow” vents that are on the top of the sloping roof surface near the soffit/eave area.
  3. Focus on the other ventilation you have in the attic.