After you hand over the leather bag that you found at the abandoned camp site, Roseline asks you to warn other sentries.
This quest is only available if you started the game in Gridania, and you have completed the quest In the Grim Darkness of the Forest.
Starting the Quest
Talk to Roseline in the Central Shroud to begin the quest.
Show the Message to Elmar
Go east to the Bannock and talk to Elmar, and hand over Roseline's Missive to get Elmar's signature.
Show the Message to Bernard
Go south to Bentbranch Meadows and talk to Bernard, and hand over Roseline's Missive to get his signature.
Show the Message to Eylgar
Go west to the stables and talk to Eylgar, and hand over Roseline's Missive to complete the quest.
Next Main Scenario Quest
After completing the quest, you will need to be at least level 12 to proceed to the next quest. After you reach level 12, talk to Eylgar to accept the next quest: Migrant Marauders.