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\begin{document}$$D$$\end{document} be a finite and simple digraph with vertex set V(D)\documentclass[12pt]{minimal}
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\begin{document}$$V(D)$$\end{document} and arc set A(D)\documentclass[12pt]{minimal}
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\begin{document}$$A(D)$$\end{document}. A signed Roman dominating function (SRDF) on the digraph D\documentclass[12pt]{minimal}
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\begin{document}$$D$$\end{document} is a function f:V(D)→{-1,1,2}\documentclass[12pt]{minimal}
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\begin{document}$$f:V(D)\rightarrow \{-1,1,2\}$$\end{document} satisfying the conditions that (i) ∑x∈N-[v]f(x)≥1\documentclass[12pt]{minimal}
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\begin{document}$$\sum _{x\in N^-[v]}f(x)\ge 1$$\end{document} for each v∈V(D)\documentclass[12pt]{minimal}
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\begin{document}$$v\in V(D)$$\end{document}, where N-[v]\documentclass[12pt]{minimal}
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\begin{document}$$N^-[v]$$\end{document} consists of v\documentclass[12pt]{minimal}
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\begin{document}$$v$$\end{document} and all in-neighbors of v\documentclass[12pt]{minimal}
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\begin{document}$$v$$\end{document}, and (ii) every vertex u\documentclass[12pt]{minimal}
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\begin{document}$$u$$\end{document} for which f(u)=-1\documentclass[12pt]{minimal}
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\begin{document}$$f(u)=-1$$\end{document} has an in-neighbor v\documentclass[12pt]{minimal}
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\begin{document}$$v$$\end{document} for which f(v)=2\documentclass[12pt]{minimal}
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\begin{document}$$f(v)=2$$\end{document}. The weight of an SRDF f\documentclass[12pt]{minimal}
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\begin{document}$$f$$\end{document} is w(f)=∑v∈V(D)f(v)\documentclass[12pt]{minimal}
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\begin{document}$$w(f)=\sum _{v\in V(D)}f(v)$$\end{document}. The signed Roman domination number γsR(D)\documentclass[12pt]{minimal}
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\begin{document}$$\gamma _{sR}(D)$$\end{document} of D\documentclass[12pt]{minimal}
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\begin{document}$$D$$\end{document} is the minimum weight of an SRDF on D\documentclass[12pt]{minimal}
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\begin{document}$$D$$\end{document}. In this paper we initiate the study of the signed Roman domination number of digraphs, and we present different bounds on γsR(D)\documentclass[12pt]{minimal}
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\begin{document}$$\gamma _{sR}(D)$$\end{document}. In addition, we determine the signed Roman domination number of some classes of digraphs. Some of our results are extensions of well-known properties of the signed Roman domination number γsR(G)\documentclass[12pt]{minimal}
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\begin{document}$$\gamma _{sR}(G)$$\end{document} of graphs G\documentclass[12pt]{minimal}
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\begin{document}$$G$$\end{document}.
