  We study the R\'enyi entanglement entropies along the massless
renormalisation group flow that connects the tricritical and critical Ising
field theories. Similarly to the massive integrable field theories, we derive a
set of bootstrap equations, from which we can analytically calculate the twist
field form factors in a recursive way. Additionally, we also obtain them as a
non-trivial roaming limit of the sinh-Gordon theory. Then the R\'enyi
entanglement entropies are obtained as expansions in terms of the form factors
of these branch point twist fields. We find that the form factor expansion of
the entanglement entropy along the flow organises in two different kind of
terms. Those that couple particles with the same chirality, and reproduce the
entropy of the infrared Ising theory, and those that couple particles with
different chirality, which provide the ultraviolet contributions. The massless
flow under study possesses a global $\mathbb{Z}_2$ spin-flip symmetry. We
further consider the composite twist fields associated to this group, which
enter in the study of the symmetry resolution of the entanglement. We derive
analytical expressions for their form factors both from the bootstrap equations
and from the roaming limit of the sinh-Gordon theory.
