All airplanes roll coincident with yaw, because as you stated the outer wing is accelerated, gains lift, and the innerwing slowed down, losing lift. With a swept wing this is worse because the effective aspect ratio changes and the outer wing becomes less swept and the inner wing more swept, further degading oscillatory stability. the solution is a big tail fin, but this can really degrade your spiral qualities (under banking, neutral or over banking qualities) because the large fin wants to continuosly "coordinate" the steepening turn and therefore send you into a spiral dive, past a 25-30 deg bank angle. However, some aircraft with large fins have both decent spiral qualities and no dutch roll... but only Boeing knows how they've accomplished that with those particular beast
. Generally, dutch roll is worse at high speed and high altitudes though not always (US Air Boeing 737 accident after yaw damper failure and a few more), however LONG TERM spiral stability is ususally improved at high altitude, high Mach number flight ironically because of the degraded tail effectiveness; these two stabilities are a tradeoff of one another... and both can lead to a nasty dive into the terra firma.