there's not a specific roast level for Turkish coffee and I believe there shouldn't be. But here in Turkiye roasters
generally prefer 2 types of roast.
a) as soon as first crack starts you stop roasting (and most people claim that's genuine Turkish Coffee)
b) you keep roasting even after second crack ends which is dark french roast (and they call it double roasted)
If we are to talk about "real traditional" then we have to go back to 15th-16th century. At those times coffee from Yemen roasted with long armed small sized iron plates, instantly roasted (dark), ground and brewed per serving. Roasting degree was an excuse for Sheikhulislam, cos this beverage was causing more problems than they predicted. Coffee was the reason people gathered in coffee houses, drinking, chatting about things "they shouldn't" including political and rebellious discussions against sultan etc. So Sheikhulislam (with the permission of Sultan) made a statement saying "any kind of food, roasted to degree of coal is prohibited by islam" by this statement the next day all coffee sacks from Yemen poured into bosphorus, which resulted in 22 years of coffee banishment

But eventually people found an excuse for Sheikhulislam's statement, they started roasting lighter
If we are to talk about last 100-150 years of Turkish Coffee and if we should take that era as our basis then we have to refer to Kuru Kahveci Mehmet Efendi, who turned coffee selling into a huge business. KKME absolutely changed almost everything about turkish coffee, including roasting style and grinding by selling pre-roasted and pre-ground. Till that time people used to roast and grind on their own, mainly mortar&pestle and centrifugal mills used accompanied with fine sieve for sifting coarser grinds which not suitable for turkish coffee (greek coffee story related to that fact actually)... then came wooden mills followed by brass hand mills. Through the end of the first World War and after some 50 more years many other things changed "again". KKME did some clever moves and used the embargo and political issues to their benefit, also coffee from yemen cost too much, they started importing coffee from Brasil and soon became a monopoly. Result? Now in Turkiye we are drinking genuine GARBAGE from Brasil (Rio Minas Grade 4 to be more precise).
The only difference between greek and Turkish, coffee used for Turkish coffee is a little coarser (just a little). So.. do as you wish.. Turkish or Greek or Bosnian or Arabian Coffee.. they are all just "brewing styles" nothing more, you can use whatever roast degree you want, all beans from all origins, even blends, be creative. There's no tradition fradition mradition into it. If we were to go back to roots then we would be measuring by hand and eye, roasting to charcoal degree, using small plates for roasting, grind between 2 stones, brewing over hot embers and consuming at that instant, no drums or poppers, no degassing, no electric, no gas stove etc. Rituals change. Even today with needs changing and demands increasing from coffee consumers, electric and electronic Turkish coffee brewers are on market, god knows what will happen in 10 years time or 20 or 30. Traditional my (_._) IMHO nothing more than a marketing word.