OK, I solved it by a double install of librocket, one in the thirdparty directory of Panda source codes, the other one is from the .deb file by JornS.
It’s weird, but it worked. My first try was having only librocket installed in my system and makepanda didn’t find them. My second try was having librocket in the thirdparty directory of the Panda codes.
Thanks rdb. 