This seems to be an official, ceremonial, Princely welcome to the castle for Rosencrantz and Guildenstern. He is, after all, welcoming these guys to a place they’ve already been welcomed by the King and Queen. He’s giving them the run of his palazzo, which they already have been given access to.
What he’s not doing is welcoming them to his chambers, or his private smoking room, or the corner of the castle that’s like his pub, you know where he can kick back and have a few drinks with buddies. He’s not welcomed them to play pool or go shooting or ride his horses. It’s like the welcome he’d give a visiting ambassador, not the welcome he gives his friend, like Horatio, for example.