In a statement, Liontrust said it would launch a Strategic Bond Fund, High Yield Bond Fund and Absolute Return Bond Fund following the pair's arrival, subject to regulatory approvals.
The announcement comes a day after Kames confirmed the duo were leaving the firm and it was reshuffling its fixed income desk.
John Ions, chief executive at Liontrust, said: “David and Phil will be an excellent addition to our existing seven fund management teams, and we look forward to promoting them to our client base in the UK and Continental Europe.
“David and Phil’s investment style means their funds provide diversification away from many of the other popular fixed income funds. Another attraction for us is the fact that David and Phil have a strong investor following, particularly among intermediary clients in the UK.
“The recruitment of David and Phil will not only expand our fund management capability but also strengthen further our fixed income proposition. Their investment style complements that of our Sustainable Fixed Income team of Stuart Steven, Kenny Watson and Aitken Ross.”
Roberts and Milburn (pictured) will join Liontrust’s Edinburgh office in early 2018.
Roberts was previously head of the fixed income at Kames Capital, and Milburn was head of investment strategy for the team.
As a result of their departure, Stephen Snowden and Adrian Hull have been appointed as co-heads of fixed income.
Jason Hollands, managing director of business development and communications at Tilney, described the hire as a "real coup" for Liontrust.
He said: "It represents another milestone in the build out of the Liontrust business beyond its historic equities focus following on from the recent Alliance Trust Investments acquisition.
"If it can successfully attract assets into fixed income strategies this will also help diversify its revenue base and reduce the concentration of its book in its hugely successful Economic Advantage products.
"Liontrust is without doubt a business going places with strong performance, a clear model of allowing each team to develop and own their own processes and a step by step approach to expansion."