Riski played his first game for TPS Turku in the Veikkausliiga when he was only 16 years old. On January 2011, the midfielder joined Polish club Widzew Łódź on three-and-a-half year contract.
On 30 August 2011, he was loaned for six months to Örebro SK in Sweden. On 12 September Riski made his Allsvenskan debut playing 90 minutes and scoring once against AIK. On 5 January 2012, he signed a three-year contract with freshly promotedHønefoss BK.
On 30 December 2013, he signed a four-year contract with Norwegian side Rosenborg BK.
On 5 August 2015 he was loaned for five months to IFK Göteborg in Sweden.