Preheat the oven to 350 degrees. In a large, ovenproof skillet, melt the butter over medium-high. Add the flour and cook, whisking, until golden, 1 to 2 minutes. Slowly whisk in the stock, then the rosemary. Simmer, whisking often, until the mixture thickens, about 5 minutes. Whisk in the cream, then stir in the peas, chicken and vegetables. Bring to a simmer; season with salt and pepper.
Meanwhile, bake the biscuits according to package directions, removing them from the oven about 5 minutes before they're done. Arrange the partially cooked biscuits on top of the chicken mixture and bake until the biscuits are golden and cooked through, about 5 minutes more.