In this paper, we investigate a cross-layer routing framework for centralized multi-hop cognitive radio networks in TV white spaces. Our Cross-layer routing focuses on joint spectrum allocation and power control. The problem is mathematically modeled as mixed integer nonlinear program that requires an appropriate solution methodology. We examined a solution based on nonlinear terms relaxation in conjunction with Branch-and-Bound algorithm. The operation, effectiveness and performance of the proposed technique are evaluated through analysis and simulations under various working conditions. The obtained numerical results indicate the benefits of the proposed technique in terms of channel assignment, flow rate, and the assigned power level for each link.