The controlling factor with streaming is the connection speed from your ISP. Upgrading your wifi is unlikely to help if your service is to slow to start with. Roku recommends a minimum of 1.5Mbps for SD. 3Mbps is better, but you need 5 or 6Mbps for reliable HD streaming.
No, I don't work for Roku.
OTA Antenna, "Netflix Player" N1000X, XDS 2100X (premature death by lightning)
Roku2 XD 3050X, Roku2 XS 3100R