  We present a general slow-roll formalism within braneworld-motivated
cosmologies with non-standard effective Friedmann equations. Full towers of
parameters involving either the inflaton potential or the Hubble parameter are
constructed and the dynamics of non-tachyonic and tachyonic fields are
considered in detail; exact cosmological solutions and the inflationary
attractor condition are provided. We compare scalar-driven and tachyon-driven
accelerating eras through slow-roll correspondence and the observational
imprint on early-universe structures.
