Both players will link up with former Wolves head coach Kenny Jacket until the end of the season with the aim of gaining some first team experience.
The Ireland U-21, Ronan, hasn't featured for Wolves first team since October with his last appearance being in the defeat to Manchester City in the Carabao Cup on penalties.
Since then, he has made a number of appearances for Scott Sellars' Under 23s side but now has the opportunity to get some more first team experience at Portsmouth.
Deslandes has featured three times so far for Wolves this season - twice in the Carabao Cup and once as a substitute away at Nottingham Forest.
The 20 year old spent the second half of last season on loan at Bury and will now hope to gain some more first team experience at Fratton Park.
