Here is programming solution for this problem.
+------------+-------------------------+
| # of Rolls | Expected Turn to Finish |
+------------+-------------------------+
| 1 | 1920.53 |
| 2 | 1112.55 |
| 3 | 910.14 |
| 4 | 89.14 |
| 5 | 78.79 |
| 6 | 78.66 |
| 7 | 78.92 |
| 8 | 89.27 |
| 9 | 89.52 |
+------------+-------------------------+
The table above shows if you roll
6 times without thinking the outcome of the rolls at the end, your chance to win is the highest with $7.66$$8.66$.
But if we consider stopping rolling after some sum values we got, let's see if something changes or not: https://pastebin.com/mSPgCi9m
I put # as the number of rolls to stop rolling, stop as stopping rolling after some values for your roll you got, and expected values for those.
As a result,
regardless of # of rolls, just roll until you get at least total roll value of $17$ then stop rolling, otherwise continue rolling seems the optimal way to play this game, which makes the game to win as expected around $7.32$$8.362$ turn.
with the little tweak as @Jaap Scherphuis suggested, I tried a couple of tricks for the end value where you get close to 50 with some threshold value, and found that having
at least total roll value of $16$ then stop rolling, with little tweak where you continue rolling if you are $47$, gets us $8.345$.
still little improvement though :)