Unlike our American Cousins we here in the EU enjoy far better (and indeed longer) warranty protection
Thus, on the assumption that your seller was based in France (where I am making the assumption you reside) your "Purchase-Contract" is with them, and it is their responsibility to resolve this situation . . . . Roku are not directly involved with your claim.
Regrettably, it is most likely that you can also expect a similar scenario with the unit purchased from Amazon.fr - so ensure you hang-on to your dated invoice as 'proof-of-purchase'
As SuzieQ chose to politely point out, the R1000 has a history of poorly manufactured power supplies, however I certainly would have been far more blunt about the lack of quality and suspect methodology of construction of same.