Heat butter in a saucepan over low heat; gradually stir flour into melted butter until smooth and bubbly, 2 to 4 minutes. Add salt; stir to combine. Remove from heat; gradually stir in milk until smooth.
Return white sauce to stovetop; bring to a boil. Reduce heat and simmer over low heat.
Cook and stir prosciutto and figs in a non-stick pan over medium heat until warm, about 5 minutes. Stir lemon zest and lemon pepper seasoning into the white sauce. Serve figs and prosciutto atop sauce.