Theres about a dozen ways to set resolution.
With KDE I guess we could use kscreen-doctor … heres a quick one-liner I cooked up for you:
mimon=$(xrandr | grep " connected" | cut -d' ' -f1); echo "Active screen recognized as "$mimon""; echo ""; echo "Desired resolution? (example: 1920x1080)"; read mires; kscreen-doctor output."$mimon".mode."$mires"@60