The Amazon Big Spring Sale is in full swing, but it isn't the only way to score discounts. If you like saving on services such as AMC Plus, MGM Plus and Starz, you can check out Roku streaming deals. Not through April 7, you can nab savings on a stack of Roku Channel premium subscriptions, which are a similar offering to Prime Video's add-on subscriptions. You can sign up for these streaming service deals on your Roku device. AMC Plus, MGM Plus and Starz on the Roku Channel are discounted to just $3 per month for one or two months, and more premium subscriptions on sale include Hallmark Plus and HiDive. Most of the deals below are Roku Channel add-ons, but you can snag the Frndly TV discount in the Frndly TV app on your Roku device. If you're open to some streaming savings, here's what Roku has to offer. These discounts expire after April 7. You must sign up through Roku to get these deals. AMC Plus on The Roku Channel: $3 per month for two months with ads. $5 per month for two months for Premium.…