Darcy–Weisbach is useless until something hands you $f$. Three relations will, and picking the wrong one is not a small error — it is an order of magnitude.

Below about $Re = 2300$ the flow is laminar: it slides in concentric sleeves, and the wall's texture never enters the argument. Then $f = \dfrac{64}{Re}$ — f equals sixty-four over Re — where $Re$ is the Reynolds number, a bare ratio of inertia to viscosity, and 64 is a constant fixed by the parabolic velocity profile of a round pipe. No roughness. No material. Just the number.

Above about 4000 the flow is turbulent and the wall does matter. The reference curve is Colebrook–White, $\dfrac{1}{\sqrt{f}} = -2\log_{10}\!\left(\dfrac{\varepsilon}{3.7D} + \dfrac{2.51}{Re\sqrt{f}}\right)$, and every Moody diagram ever printed is a plot of it. Here $\varepsilon$ — epsilon — is the absolute roughness of the wall in metres (0.045 mm for new commercial steel, 0.26 mm for aged cast iron), and $\varepsilon/D$ is the relative roughness, a bare ratio. Look closely: $f$ appears on BOTH sides. It cannot be rearranged into an answer, only iterated toward one.

So the working world uses Swamee–Jain, $f = \dfrac{0.25}{\left[\log_{10}\!\left(\dfrac{\varepsilon}{3.7D} + \dfrac{5.74}{Re^{0.9}}\right)\right]^{2}}$, which is explicit — everything on the right, $f$ alone on the left — and lands within about 1% of Colebrook across the whole turbulent field. Say plainly what it is: an approximation to Colebrook, not a rival theory. If a paper asks for Colebrook and you hand back Swamee–Jain, say so.

One nugget. Between 2300 and 4000 lies the transition, where flow flickers between the two and no correlation is trustworthy. Designers do not size there on purpose; they step the pipe until they are safely out of it.