Tomkins, who made his Wales debut earlier this year under new boss Wayne Pivac, was being lined up to join Australian Joe Tomane in midfield but the deal to bring the released Leinster back to Newport has now stalled.
That has resulted in Roberts, whose most recent rugby was earlier this year in the colours of the Stormers in South Africa, negotiating with the Dragons about a return to regional rugby in Wales.
The 94-time Wales cap Wales returned home just before the Covid-19 lockdown hit South Africa and he has been helping the NHS during the pandemic as a qualified doctor. Roberts became involved with the Cardiff and Vale Health Board in an honorary role.
"There will be times where we face the stark reality of the bigger clubs… but you cannot move Dragons from where they have been without at some stage being exposed"
— RugbyPass (@RugbyPass) July 9, 2020
The potential arrival of Roberts, who played for Cambridge University in the 2015 Varsity match, would add much-needed experience to the Dragons squad which has been strengthened by the arrival of Tomkins and Jonah Holmes, the Wales wing, who arrived from Leicester.
Dean Ryan, the Dragons director of rugby, is heading the negotiations with Roberts who started his senior career at Cardiff RFC and was a key figure in the series-winning Lions squad in Australia in 2013.
Roberts won the last of his Wales caps against New Zealand in 2017, but the 6ft 4in centre showed in the Stormers colours that he remains a potent force. Aside from Guinness PRO14 duty, his experience would prove useful when the Dragons play in the expanded 24-team Heineken Champions Cup next season.
They are currently awaiting a 2019/20 Challenge Cup quarter-final away to Bristol this September, a fixture that would see Roberts up against Fiji’s Semi Radradra who has joined the big-spending West Country outfit.
In other Dragons news, back row Ben Fry, 21, has committed his long-term future after putting pen to paper on a first professional contract with the region. Younger brother Harry, 19, is also becoming a Dragon as the prop will make the move from Gloucester where he was part of the academy set-up.
'We have the best training centre in the country and that is not bragging, that is just factual'@BristolBears CEO Mark Tainton on their new training centre, ring-fencing, Lam, Radradra & how a clean-out of players in 2017 was needed, writes @heagneyl https://t.co/fsHrkGupXc
— RugbyPass (@RugbyPass) July 12, 2020
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