Former Borussia Dortmund defender Mats Hummels is joining Serie A side Roma, the club announced Wednesday on X. “Hi Giallorosso fans, this is Mats, a new player,” Hummels said in a video published by Roma. “I’m really happy to play for this club in front of you and see you in the stadium.” Hummels arrived in Italy earlier on Wednesday to sign a contract with the Italian side, broadcaster Sky reported. Roma did not specify the length of the contract, but according to transfer expert Fabrizio Romano, it is expected to be for one year. Hummels will be given the shirt number 15. A video published …