Roizman is one of the most visible and charismatic opposition figures in Russia.
A critic of the Kremlin and former mayor of Russia's fourth-largest city was on Wednesday arrested on charges of discrediting the country's military.
Yevgeny Roizman, 59, says he was detained for calling the Ukraine war an invasion.
Moscow insists it should be called a "special military operation".
Roizman served as the mayor of Yekaterinburg from 2013 to 2018 and is one of the most visible and charismatic opposition figures in Russia.
Roizman told reporters he was charged under a new law adopted after Russia sent troops into Ukraine on 24 February. He faces up to five years in prison if convicted.
A Russian court ordered for Roizman to be released on Thursday but barred him from public events or communicating with anyone other than his lawyers and close family.
Russian courts fined Roizman three times earlier this year on similar charges, paving the way for a criminal case the law authorises for repeat offences.
His arrest triggered protests in his support, and one demonstrator was detained and ordered to serve 15 days in jail.
Cautious words of support also came from Roizman's longtime political rival, the governor of Russia's Sverdlovsk region.
“We used to be and continue to be political opponents. The law is the law. But, like any person, he deserves fairness and respect, and I hope he gets them,” Gov. Yevgeny Kuyvashev said in a video statement posted on Telegram.
Days after Russian President Vladimir Putin sent troops into Ukraine, Russia's Kremlin-controlled parliament controlled approved legislation that outlawed disparaging the military and the spread of “false information” about the military operations in Ukraine.
Russian courts have increasingly handed out fines and, occasionally, prison terms to critics of Moscow's action in Ukraine.
According to Net Freedoms, a legal aid group focusing on free speech cases, there were 79 criminal cases as of mid-August on charges of spreading false information about the military and up to 4,000 administrative cases on charges of disparaging the armed forces.
Pavel Chikov, a leading Russian human rights advocate, said on Wednesday that Russian courts have so far heard 3,500 administrative cases for discrediting the military and found most defendants guilty. All of them could face criminal charges like Roizman if they speak out again against Russia's operation in Ukraine, Chikov noted.
Until his arrest, Roizman remained one of the most visible opposition figures in Russia who had not been jailed or fled the country under pressure from authorities. Two other prominent opposition politicians, Ilya Yashin and Vladimir Kara-Murza were arrested under the same law as Roizman and face up to 10 years in prison if convicted.
Similar charges were recently brought against eight close associates of imprisoned opposition leader Alexei Navalny. All of them have left Russia after they became the subjects of multiple criminal investigations.