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While roton dispersion relations had been restricted to correlated quantum systems at low temperature, recent works show the possibility of obtaining this unusual dispersion in acoustic and elastic metamaterials. Such phenomenon has been demonstrated in periodic structures by means of beyond-nearest-neighbour interactions, following the formulation firstly developed by Brillouin in the ′ 50 s. In this paper, we demonstrate both numerically and experimentally that beyond-nearest-neighbour connections are not a necessary condition to obtain this unusual dispersion relation in elasticity. Leveraging the intrinsic complexity of elastic systems supporting different types of waves, we demonstrate that mode locking can be applied to obtain roton dispersion, without the need of elastic or magnetic interactions between non nearest neighbours. Moreover, the combination of roton dispersion and rainbow physics enables spatial separation of the energy fluxes with positive and negative group velocity. • Development of a periodic structure with roton-like dispersion without implementing long range interactions. • Roton-like dispersion using locking coupling mechanisms between counter propagating waves in periodic arrays. • Graded roton-like structure for achieving a double Rainbow trapping effect. • Numerical and experimental validation of all the above statements. [ABSTRACT FROM AUTHOR]