A Roman dominating function(RDF) on a signed graph S = (G, σ) is a function f : V (S) → {0, 1, 2} such that (i) f(N[v]) = f(v) + ∑u∈N(v)σ(uv)f(u) ≥ 1 for every vertex v ∈ V (S) and (ii) for any vertex v with f(v) = 0 there ...