Come The Spring by Julie Garwood.  
A single-volume collection brings together the entire Clayborne saga, including For the Roses, One Pink Rose, One White Rose, and One Red Rose.   Cole Clayborne has been tricked into accepting a badge and the title of U.S. Marshal by Sheriff Marshall Ryan. He would refuse the badge if he could, but the Blackwater Gang is up to no good and Cole feels compelled to help.