ᐅ Insulation between rafters with rigid/flexible mineral wool batt

Hello, I couldn’t find any clear information about this online. Here is my situation:
I have an attic that is currently used only as storage and cannot be converted into a living space due to low headroom. I am looking for a way to insulate my attic with minimal loss of height.
Current roof structure:

• Corrugated fiber cement sheets
• Counter battens
• Battens
• Roofing felt
• Boards
• Rafters

Can I roughly say that I can place insulation batts between the rafters without a vapor barrier? I cannot insulate the roof ridge because I don’t have access to it.
Since the roof was replaced a few years ago, removing and reinstalling the roofing is not planned.