A: You do have an option that will work and be safe. What you need is a recessed lighting fixture that carries an “IC” rating. These letters stand for “insulation contact”, and it means that no clearance is necessary around the light fixture itself. Non-IC recessed lights typically require a minimum of three inches of separation from insulation materials because of the heat generated.
At least as important in your case is that IC fixtures are designed to be airtight. This detail stops the upward migration of warm, moist indoor air into cathedral ceiling spaces and this is key. Without this feature, damaging levels of condensation would certainly develop in your roof frame during winter if you live in a cold climate, causing water damage, rot and a big reduction in thermal performance. I often hear from homeowners who have water damage every spring from frost that developed in cathedral ceilings during winter and melts in the spring. Non IC recessed light fixtures are often the part of this problem.
When you’re choosing an IC fixture, consider a model that takes LED bulbs and requires no electrical box mounted to the wood frame of the house. Since about 2010, very inexpensive, high-quality recessed fixtures have become available that simply grip into a hole cut in drywall. I’ve bought and used these and they work perfectly. The older style of recessed fixtures that you see to the left might cost $50 to $100 each, but you can buy “boxless” fixtures for $10 or $15 each online. Click to see the latest batch I bought on Amazon. I installed a couple of dozen in a house I built and they work great.