There is no current Roku player with analog or separate digital outputs. Unless you want to upgrade your AVR (and honestly, it's time), you would need an HDMI audio splitter. But even then you might have a problem, as most online streaming providers use Dolby Digital Plus (EAC-3) as their preferred codec. You would have to ensure your HDMI audio splitter can convert DD+ to analog.
I realize your projector isn't even 1080p, but with such great speakers you'd really do well to upgrade to an AVR with HDMI inputs and support for the latest codecs, such as Dolby TrueHD and DTS Master Audio. Most Blu Ray discs all have one of those audio codecs, and yes they are a noticeable improvement over any analog Dolby sound you now have. I paid well under $500 (I think it was around $380) for a Yamaha AVR that supports all the latest audio codecs, including Dolby Atmos and DTS:X, and has HDMI 2.1 ports that even support Dolby Vision. You don't have to spend a fortune for a reasonable AVR.
Dan
Roku Community Streaming Expert
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