Having no idea that he might need to speak until that morning, Ron spent the time while they were waiting for everyone to arrive trying to figure out words to say. And then he'd gone up, in front of everyone, and froze.
He couldn't put into words what his parents had meant to him, what his family meant to him. He couldn't voice aloud how much he missed them. So he stood frozen in place, feeling awkward and overwhelmed,until he finally managed to speak a few words.
"I was lucky," Ron had muttered to the crowd. "Didn't realise just how lucky. Until..." He looked over at the caskets, and said "Mum, Dad. I miss you."
And then he'd quickly fled from the spotlight, back to his seat next to Hermione.
By the time the Wake had rolled around, Ron was exhausted, but he preferred the atmosphere. Stories were being traded, and that was a lot better than staring at the coffins that contained his parents. So he was listening to the tales being told, and enjoying other peoples memories of his parents. It was like grasping at the last remaining traces of their lives.