'It's all I think about,' the singer tells MTV News of hitting the road after opening on Rihanna's Last Girl on Earth Tour.By Jocelyn Vena, with reporting by Christina Garibaldi Ke$ha Photo: MTV News Ke$ha is currently on the road with Rihanna, but the "Tik Tok" singer says once the Last Girl On Earth Tour wraps up, she'd like to plot a trek of her own.