Sienna Miller can roll solo. The star was spotted at the opening of TriBeCa restaurant Los Americanos waiting alone for her pal, night-life guru Nur Khan, for 20 minutes. Spies said she happily texted on her phone and smiled at passersby. Perhaps Miller’s getting used to nights alone since her fiancé and baby daddy Tom Sturridge is onstage in Broadway show “Orphans.” Miller was just nominated for a BAFTA TV award for HBO movie “The Girl.” Maggie Gyllenhaal and Peter Sarsgaard also attended the Americanos bash.