Not buying that. If I'm a new user and put up a post, it gets buried by 3-40 PAGES of spam. 1: my question isn't going to get attention anyway and 2: do I really trust the place if it can't control spam? The answer to both is NO. Enabling post/comment moderation once the user has X amount of approved posts they can post till the end of time. Almost all forum software has these functions. flower, I'd bet 95% of spam would be eliminated by requiring 3 days and 1 single approved post before being able to post fully.
With two people on staff they should be able to approve new poster posts pretty quickly. Over night doesn't really matter.
Roku has decided that it's in their interest to allow new users to post, to avoid same-day returns ("I tried to get help, but it wouldn't even let me ask a question!") If they felt it was in their financial interest to not allow new users to ask questions, they would.
You also seem to overlook the latest trick spammers are pulling: copy-pasting questions from Reddit, then editing them days later to include spam links. That right there gets around your suggestion. That's not to trash your suggestion, but to say that no matter what you do, as long as they have a single moderator (that's Tanner, since Shawn is gone), and until they user better software or better spam plugins, nothing will stop the spam. Roku has decided that they'd rather not add to the issues by not allowing new users to post. Right or wrong. I understand it. And, if I was hamstrung by corporate the way the moderators (Shawn, and now Tanner) have been, I don't know that I would turn off new user posts, at least if I didn't know that I could easily and quickly approve them. There are 168 hours in a week. If Tanner is working 40 solid on the Forum, that's still 128 minutes (over 3 times as much) that isn't manned. And there's no way he's putting in a full 40 just on the Forum.