Screeps Road calculator (untested)

// Road Calculator
var roads = function (){
    var queue = {};
    for(var r1 in Game.rooms){
        // dont execute when theres more than 50 construction sites
        if(Game.constructionSites.length > 50){return}

        // 1. Connections between rooms (from controller to controller or 25,25 of each room)
        var r1_pos = new RoomPosition(25,25,r1);
        var r1_coords = roomCoordinates.nameToCoordinates(r1);
        if(Game.rooms[r1].controller){
            r1_pos = Game.rooms[r1].controller.pos;
        }
        for(var r2 in Game.rooms){
            var r2_coords = roomCoordinates.nameToCoordinates(r2);
            if(Math.abs(r1_coords.x - r2_coords.x) + Math.abs(r1_coords.y - r2_coords.y) !== 1){ //if the rooms are not adjecant to eachother (or identical) continue with the next pair
                continue;
            }
            var r2_pos = new RoomPosition(25,25,r2);
            if(Game.rooms[r1].controller){
                r2_pos = Game.rooms[r2].controller.pos;
            }

            var path = PathFinder.search(r1_pos,r1_pos).path;

            for(var i in path){
                var tile = Game.rooms[path[i].roomName].lookAt(path[i].x,path[i].y)
                if(tile.terrain === "plain"){
                    queue.push(path[i]);
                }
            }
        }
        // 2. from controller to storage
        if(Game.rooms[r1].storage){
            var path = PathFinder.search(Game.rooms[r1].controller.pos,Game.rooms[r1].storage.pos).path;
            for(var i in path){
                var tile = Game.rooms[path[i].roomName].lookAt(path[i].x,path[i].y)
                if(tile.terrain === "plain"){
                    queue.push(path[i]);
                }
            }
        }
        //3. from controller to other structures
        var structures = Game.rooms[r1].find(FIND_STRUCTURES,{
            filter:(structure)=>{
                return structure.my && (
                    structure.structureType === STRUCTURE_EXTENSION ||
                    structure.structureType === STRUCTURE_SPAWN ||
                    structure.structureType === STRUCTURE_EXTRACTOR
                )
            }
        });

        if(structures){
            for(var structure in structures){
                var path = PathFinder.search(Game.rooms[r1].controller.pos,structures[structure].pos).path;
                for(var i in path){
                    var tile = Game.rooms[path[i].roomName].lookAt(path[i].x,path[i].y)
                    if(tile.terrain === "plain"){
                        queue.push(path[i]);
                    }
                }
            }
        }
        //4. from controller to sources
        var sources = Game.room[r1].find(FIND_SOURCES)

        if(sources){
            for(var source in sources){
                var path = PathFinder.search(Game.rooms[r1].controller.pos,sources[source].pos).path;
                for(var i in path){
                    var tile = Game.rooms[path[i].roomName].lookAt(path[i].x,path[i].y)
                    if(tile.terrain === "plain"){
                        queue.push(path[i]);
                    }
                }
            }
        }
        //4. from sources to extensions
        var extensions = Game.rooms[r1].find(FIND_STRUCTURES,{
            filter:(structure)=>{
                return structure.my && structure.structureType === STRUCTURE_EXTENSION
            }
        });

        for(source in sources){
            for(extension in extensions){
                var path = PathFinder.search(extensions[extension].pos,sources[source].pos).path;
                for(var i in path){
                    var tile = Game.rooms[path[i].roomName].lookAt(path[i].x,path[i].y)
                    if(tile.terrain === "plain"){
                        queue.push(path[i]);
                    }
                }
            }
        }

        //Set ConstructionSites
        for(var i in queue){
            Game.rooms[queue[i].roomName].createConstructionSite(queue[i].x,queue[i].y,STRUCTURE_ROAD);
        }

    }
}