Rock bottom oil prices, a resurgent ruble and a rebounding stock market make it a good time to invest in Russia, according to American investor Jim Rogers.

"I'm very optimistic about the future of Russia," Rogers told the audience at a Moscow investment conference put on by investment firm BCS. "Certainly one of the most attractive stock markets in the world these days for me is Russia."

This may seem surprising to those who only remember last year's news about the plummeting ruble. But one of 2014's worst performing currencies has become 2015's best in the first three months of the year — rebounding to 55.3 rubles to the dollar after a low of 80 in December.

The RTS — the Russian stock index — fell in 2014 by 45% but has gained 20% in the first quarter of 2015. Rogers said this "the right place at the right time" for investing in Russia, noting that his own portfolio contains shares in the Moscow exchange and in Russian companies like the fertilizer company Phosagro and the airline Aeroflot.

Oil prices also may have bottomed out, after falling more than 50% during the last months of 2014. Though it's hard to know when exactly they will have reached their lowest point, some are optimistic that the rebound will start this coming quarter or the next.

"The first quarter is going to be, I hope, the bottom of earnings for many years to come," Fadel Gheit, an analyst at Oppenheimer told the Wall Street Journal about oil companies' difficult last two quarters.

— Charlie Bilello, CMT (@MktOutperform) April 6, 2015

Rogers was also optimistic about having reached the low point for oil prices and about a continuing rise in the stock market, making Russia a good investment, despite its difficult previous year.

"Something has happened over in the Kremlin. The old ways of doing things in Russia have changed in my view," he said.

Rogers is a veteran financier, who founded the Quantum Fund along with billionaire George Soros in the 1970s. Currently residing in Singapore, he is the chairman of Rogers Holdings and Beeland Interests, Inc.

"I'm bullish on Russia," he said in a February interview on Bloomberg TV. "Everybody hates Russia and as you know, I like to find something that's hated." Explaining that his attitude has changed after 46 years of being bearish about investments in the country, because he believes there's been a positive change in the way the country treats foreign investors.

Soros Seeks "Game-Changer" for Ukraine Instead

Rogers' former partner Soros, however, has taken a different attitude towards the region.

The billionaire financier-turned-philanthropist said in March that he was prepared to invest $1 billion in Ukraine if Western governments would help spur investment as well.

"The West can help Ukraine by increasing attractiveness for investors. A political risk insurance is necessary. This could take the form of mezzanine financing at EU interest rates — very close to zero," he said in a March interview.

"I stand ready. There are concrete investment ideas, for example in agriculture and infrastructure projects. I would put in $1 billion. This must generate a profit. My foundation would benefit from this… Private engagement needs strong political leadership."

Soros has advocated a $50 billion aid package to Ukraine from Western powers and international organizations such as the European Investment Bank, World Bank, the European Bank for Reconstruction and Development and the IMF.

"That would be a game-changer. Ukraine would embark on radical reforms and, instead of hovering on the edge of bankruptcy, it would turn into a land of promise that would attract private investment."

In an article in the New York Review of Books he called such a package "a defense expenditure by the EU countries" against Russia.

In December 2014, Ukrainian Prime Minister Arseniy Yatsenyuk called for "an international donor conference [and] the adoption of a Ukrainian recovery plan" of billions of dollars or, he claimed, the nation would face default on foreign debts.