For Russia Russo-Japanese War was a total disaster and an embarrassment that emboldened resistance groups against the Tsar. For Japan the War was a triumphant march onto the world stage and a mark of honor being the first Asian nation to beat a European one. So, make the roles be reversed. Have the Russians be able to crush Japan and force them to the table rather than the other way around. Also, what effect would that have on the history of the Pacific?
Well, neither Russia or Japan were crushed per say: Russia did suffer some really embarrassing loses at sea, true, but on land she was giving the enemy a real bloody nose. The army had to be withdrawn not because they were routing, but because Czar Nicky needed those bayonets back in St.Petersburg in order to picket his throne. Japan, also not beaten or utterly triumphant, also agreed to mediation because she was running out of money with which to finance the war despite not having achieved the hegemony over Manchuria that she desired. So, if we're going historical, reversing the roles would lead to a similarly modest peace in Russia's favor; creating a Russian hegemony over Manchuria, allowing her to keep Port Arthur, and keeping Japan off-balance enough to prevent her from formally annexing Korea 5 years later.
As far as global effects, Britain would be wringing its hands with worry: The Anglo-Japanese Alliance was supposed to be her tool to keep Russian naval expansion and projection of power further east and south in check, and Tokyo had just demonstrated that they can't effectively serve that role even when just defending their home turf on the opposite side of the world where the Ruskies just have one (barely completed) major rail line. As such, the UK is going to have to find new allies to counter the Franco-Russian Entente to prevent them from potentially gaining enough power to content British dominance on the colonial and naval-commerical front (Which are the lifelines of her wealth and power)... which conveniently times itself with the tuning down of the Anglo-German naval race and increased German interest in the Ottomans; another traditional "hedge" against Russian power (Alongside A-H, the two keep Moscow from reaching the Medd. or consolidating with its Balkan-Slavic allies). As for Japan, they're left with a beat-up navy and no money to pay for a new one and a lack of power projection onto the Asian mainland, which means they're relegated to a minor role in international affairs for the immediate future: this opens up more oppritunity/space for the Europeans to feel the need/modivation to get directly involved in the events of the Chinese Revolution and resulting civil war/warlord breakdown.
