—The enhancement of cellular networks with relaying technologies is expected to bring significant techno-economic benefits, but proper allocation of resources may be a challenging task. This paper addresses the question whether cross-layer optimization is essential for obtaining the expected relaying benefits. We present a network dimensioning approach based on joint routing and radio resource allocation. We consider a macro-cellular scenario with a max-min user-rate objective. If a single route per source is fixed, rates and time-shares can be optimally allocated to each link. In a simple macro-cellular propagation environment, the relays must cost at most 10-25% of a base station cost, if the network is deployed at once. The results are only slightly better when the routing is included in the joint resource allocation.