I don't recall the Roxanne being sold as a dead-flat, reference studio monitor either. Still, even though my Roxanne custom is not dead-neutral to my ears, it is certainly neutral-ish with its bass turned to its flattest (lowest) position. I go to Chesky Records' recording sessions when I can, and was at one a couple of weeks ago. I was traveling very light, so only took IEMs with me.
For monitoring during recording, I chose the Roxanne; and going back and forth from the live performances to the studio, the Roxanne was an outstanding monitor, both tonally, and where imaging was concerned.
Mimouille, it's clear you're obviously
very upset over the Layla's release. My advice is to enjoy your Roxanne, as it's an amazing headphone, and not regret your purchase of it if you're otherwise happy with its performance.
The Layla is not priced similarly to the Roxanne--it's nearly double the price of the Roxanne. (I'm not sure what the custom Layla price will be, but I'm guessing it'll be more expensive than the universal.)
For me personally, until the Layla is available in custom form, the Roxanne and the Kaiser 10 will be my current go-to IEMs.