Deployable coilable booms are extendible structures that have been used in a number of space and terrestrial applications. Fiber reinforced polymer (FRP) composite variants of these deployable booms have advantages over the metallic versions in the form of higher specific stiffness and greater design flexibility. A deployment failure mode called ‘blossoming’, in which the boom unwinds and extends within the deployment mechanism, can occur if an excessive load is applied to the boom tip. Blossoming can be mitigated by using compression rollers which radially constrain the coiled boom. An energy method is used to model the composite boom during deployment, and to predict the tip force a boom can withstand before blossoming occurs. The analytical results are compared with experimental results. The effects of the boom material properties and geometric parameters are investigated to provide more guidance in the design of deployable coilable boom systems.