Short answer - Yes, it can/does matter (depending).
"Roku Express HD" and "software up to date" and "second highest tier of Spectrum" arent specific enough, especially when seeking technical help/recommendations.
Use Settings/System/About to post the Roku model # and software version.
You likely have a 3900 or 3930 model (these are 2.4Ghz only with no wired/ethernet option)
Most of the streaming services use 3-5Mbps for SD/HD content, and 7-16Mbps for 4K, and even 25-120Mbps for 4K HDR Live sports/events.
Buffering is almost always a network bandwidth/stability issue (either within your home network, or on the internet). However, it all depends on the specific source (unknown) of the buffering.
If the current 2.4Ghz channel/settings is the problem, the manually configuring the Channel to 1/6/11 and the bandwidth to 20Mhz may solve it.
If 2.4Ghz is the source, then switching to 5Ghz might solve it - the $30 Express 4K+ with dual-band WiFi, or the $80 Ultra with dual band WiFi would solve that.
If the WiFi connection (either 2.4Ghz or 5Ghz) is the source of bandwidth constraint/instability, then switching to a wired connection would solve it - the $30 Express 4K+ with USB>Ethernet adapter, or the $80 Ultra w/Ethernet would solve that.
If the modem/router/gateway or the internet connection itself is misconfigured/unstable, these would have to be addressed to Spectrum (assuming you are using their provided equipment).
Overall, knowing nothing else, I'd recommend getting either:
1) $80 Ultra (4800)
2) $30 Express 4K+ (3941) and a USB>Ethernet adapter https://support.roku.com/article/360058027813
3) Try the 5Ghz WiFi first, and if it still buffers, use a wired/Ethernet connection.
