He becomes Sam Allardyce's third summer signing, and the first recruit to his new-look defence.
Rozehnal said: "I am really happy because my dream has come true. I have always dreamt about this competition - for me, the Premier League is one of the best in the world.
"Now it is about work and about showing everybody I am in the right place.
"For me, it will be another big step. From the Czech Republic to Belgium, from Belgium to France and now from France to the Premier League - I am really excited because I will play against the best footballers in the world.
"Now I have to show my best, and I hope I will do that."
Rozehnal, who began his career in his home country with Sigma Olomouc and arrived in France via Belgian side FC Bruges, had caught Allardyce's eye during his time at Bolton, and he is grateful that interest persisted.
He said: "I know the coach was interested in me when he was at Bolton and I am really happy he is still interested in me.
"It is really important that the coach believes in me and has given me my chance. Now it is up to me, if I work hard, to show him and my team-mates that I can get into the team.
"I am really happy that everything is done and now I am ready to prepare for next week."