Supernova Remnants (SNRs) emitting gamma rays in the GeV-TeV energy range are fundamental for identifying the accelerators of Galactic cosmic rays. In 2018 H.E.S.S. has revealed at TeV energies three extended shell-like sources: HESS J1534-571, HESS J1614-518 and HESS J1912+101. A radio Supernova Remnant (SNR) candidate has been identified as a counterpart to HESS J1534-571, therefore it is classified as a SNR, while the other two are still candidate SNRs. We will report on the Fermi-Large Area Telescope (LAT) analysis of all three sources using 10 years of Pass 8 data. We will focus mostly on the analysis of HESS J1912+101 for which we are going to present the results of a deep observation campaign with the MAGIC telescopes together with Fermi-LAT data. The Fermi-LAT observed morphology of this source is really complex and we will describe it in detail. The joint Fermi-MAGIC morphological and spectral analysis covers six decades in energy.