At first, I had some questions about why you'd use a Raspberry Pi for this, but once I realized that video was being recorded as well it made more sense. I'm quite impressed.
For increasing sample rate, it really depends on where the problem is. The Pi is recording video and managing the sensors - are these two tasks competing with each other?
Perhaps using another controller to deal with the sensors and telemetry transmission could help (if contention is actually the problem). Something like the ESP32 in the D1 Mini form factor would easily fit in the rocket. If I was doing this, I'd ignore the ESP32's onboard radios and use the LoRa module since it seems to work quite well in this application.
[0] https://johnjonesfour.com/2020/10/03/model-rocket-telemetry-...