I know that I can find an upper bound for the bank angle for a plane, if I know the maximum sustained load factor of that plane because the roll angle and the load factor $n_z$ in a turn are directly related: $$tan (\varphi) = \sqrt{n_z^2 - 1} \;\; \text{or} \;\; \varphi = arctan\left(\sqrt{n_z^2 - 1}\right)$$ And also I known that the bank angle would not be more than 30° for civilian and 75° and more for military aircraft.
But my question is :
How can one get the minimum possible bank angle an airplane can use to perform a turn with a given radius before reaching the stall speed?
Also I want to know if the stall speed is known, can we use the formula :
$$ W = V/R $$
to calculate the angular rate of turn (of course considering the level turn)?